Christianity is the most adhered to religion in the United States , with 75% of polled American adults identifying themselves as Christian in 2015.   This is down from 85% in 1990, lower than 81.6% in 2001,  and slightly lower than 78% in 2012.  About 62% of those polled claim to be members of a church congregation.  The United States has the largest Christian population in the world, with nearly 280 million Christians, although other countries have higher percentages of Christians among their populations.
All Protestant denominations accounted for 51.3%, while the Catholic Church by itself, at 23.9%, was the largest individual denomination. A 2008 Pew study categorizes white evangelical Protestants , 26.3% of the population, as the country's largest religious cohort;  another study in 2004 estimates evangelical Protestants of all races at 30–35%.  The United Methodist Church is the third largest church in the United States, and is the largest mainline denomination.  The Church of Jesus Christ of Latter-day Saints (Mormons) is the fourth largest church in the United States, and the largest church originating in the U.S.  
Christianity was introduced to the Americas as it was first colonized by Europeans beginning in the 16th and 17th centuries . Going forward from its foundation, the United States has been called a Protestant nation by a variety of sources.     Immigration further increased Christian numbers. Today most Christian churches in the United States are Mainline Protestant , Evangelical Protestant , or Catholic . 
Major denominational families
Christian denominations in the United States are usually divided into three large groups: Evangelical Protestantism , Mainline Protestantism, and the Catholic Church . There are also Christian denominations that do not fall within either of these groups, such as Eastern Orthodoxy , but they are much smaller.
A 2004 survey of the United States identified the percentages of these groups as 26.3% (Evangelical), 22% (Catholics), and 16% (Mainline Protestant).  In a Statistical Abstract of the United States , based on a 2001 study of the self-described religious identification of the adult population, the percentages for these same groups are 28.6% (Evangelical), 24.5% (Catholics), and 13.9% (Mainline Protestant). 
In typical usage, the term mainline is contrasted with evangelical .
The Association of Religion Data Archives (ARDA) counts 26,344,933 members of mainline churches versus 39,930,869 members of evangelical Protestant churches.  There is evidence that there has been a shift in membership from mainline denominations to evangelical churches. 
As shown in the table below, some denominations with similar names and historical ties to Evangelical groups are considered Mainline.
|Protestant: Mainline vs. Evangelical|
|Family:||Total: ||US% ||Examples:||Type:|
|Baptist||38,662,005||25.3%||Southern Baptist Convention||Evangelical|
|American Baptist Churches in the U.S.A.||Mainline|
|Pentecostal||13,673,149||8.9%||Assemblies of God||Evangelical|
|Lutheran||7,860,683||5.1%||Evangelical Lutheran Church in America||Mainline|
|Lutheran Church–Missouri Synod||Evangelical|
| Presbyterian / |
|5,844,855||3.8%||Presbyterian Church (U.S.A.)||Mainline|
|Presbyterian Church in America||Evangelical|
|Methodist||5,473,129||3.6%||United Methodist Church||Mainline|
|African Methodist Episcopal Zion Church||Evangelical|
|Anglican Church in North America||Evangelical|
|Adventist||2,203,600||1.4%||Seventh-day Adventist Church||Evangelical|
|Holiness||2,135,602||1.4%||Church of the Nazarene||Evangelical|
|Other Groups||1,366,678||0.9%||Church of the Brethren||Evangelical|
|Friends General Conference||Mainline|
Evangelicalism is a Protestant Christian movement. In typical usage, the term mainline is contrasted with evangelical . Theologically conservative critics accuse the mainline churches of "the substitution of leftist social action for Christian evangelizing, and the disappearance of biblical theology," and maintain that "All the Mainline churches have become essentially the same church: their histories, their theologies, and even much of their practice lost to a uniform vision of social progress."  Most adherents consider the key characteristics of evangelicalism to be: a belief in the need for personal conversion (or being " born again "); some expression of the gospel in effort; a high regard for Biblical authority ; and an emphasis on the death and resurrection of Jesus .  David Bebbington has termed these four distinctive aspects conversionism , activism , biblicism , and crucicentrism , saying, "Together they form a quadrilateral of priorities that is the basis of Evangelicalism."
Note that the term "Evangelical" does not equal Fundamentalist Christianity , although the latter is sometimes regarded simply as the most theologically conservative subset of the former. The major differences largely hinge upon views of how to regard and approach scripture ("Theology of Scripture"), as well as construing its broader world-view implications. While most conservative Evangelicals believe the label has broadened too much beyond its more limiting traditional distinctives, this trend is nonetheless strong enough to create significant ambiguity in the term. As a result, the dichotomy between "evangelical" vs. "mainline" denominations is increasingly complex (particularly with such innovations as the " Emergent Church " movement).
The contemporary North American usage of the term is influenced by the evangelical/fundamentalist controversy of the early 20th century. Evangelicalism may sometimes be perceived as the middle ground between the theological liberalism of the Mainline (Protestant) denominations and the cultural separatism of Fundamentalist Christianity .  Evangelicalism has therefore been described as "the third of the leading strands in American Protestantism, straddl[ing] the divide between fundamentalists and liberals."  While the North American perception is important to understand the usage of the term, it by no means dominates a wider global view, where the fundamentalist debate was not so influential.
Evangelicals held the view that the modernist and liberal parties in the Protestant churches had surrendered their heritage as Evangelicals by accommodating the views and values of the world . At the same time, they criticized their fellow Fundamentalists for their separatism and their rejection of the Social Gospel as it had been developed by Protestant activists of the previous century. They charged the modernists with having lost their identity as Evangelicals and the Fundamentalists with having lost the Christ-like heart of Evangelicalism. They argued that the Gospel needed to be reasserted to distinguish it from the innovations of the liberals and the fundamentalists.
They sought allies in denominational churches and liturgical traditions, disregarding views of eschatology and other "non-essentials," and joined also with Trinitarian varieties of Pentecostalism . They believed that in doing so, they were simply re-acquainting Protestantism with its own recent tradition. The movement's aim at the outset was to reclaim the Evangelical heritage in their respective churches, not to begin something new; and for this reason, following their separation from Fundamentalists, the same movement has been better known merely as "Evangelicalism." By the end of the 20th century, this was the most influential development in American Protestant Christianity.
The National Association of Evangelicals is a U.S. agency which coordinates cooperative ministry for its member denominations.
A 2015 global census estimated some 450,000 believers in Christ from a Muslim background in the USA, most of whom are evangelicals and/or Pentecostals. 
The mainline Protestant Christian denominations are those Protestant denominations that were brought to the United States by its historic immigrant groups; for this reason they are sometimes referred to as heritage churches. The largest are the Episcopal (English), Presbyterian (Scottish), Methodist (English and Welsh), and Lutheran (German and Scandinavian) churches.
Mainline Protestantism as the Episcopalians (76%),  the Presbyterian (64%),  and the United Church of Christ has the highest number of graduate and post-graduate degrees per capita,  of any other Christian denomination in the United States, as well as the most high-income earners .
Episcopalians and Presbyterian tend to be considerably wealthier  and better educated than most other religious groups in Americans, and are disproportionately represented in the upper reaches of American business ,  law and politics , especially the Republican Party . Numbers of the most wealthy and affluent American families as the Vanderbilts and Astors , Rockefeller , Du Pont , Roosevelt , Forbes , Whitney , Morgans, and Harrimans are Mainline Protestantism families. 
According to Scientific Elite: Nobel Laureates in the United States by Harriet Zuckerman , a review of American Nobel prizes winners awarded between 1901 and 1972, 72% of American Nobel Prize Laureates, have identified from a Protestant background.  Overall, 84.2% of all the Nobel Prizes awarded to Americans in Chemistry ,  60% in Medicine ,  and 58.6% in Physics  between 1901 and 1972 were won by Protestants.
Some of the first colleges and universities in America, including Harvard ,  Yale ,  Princeton ,  Columbia , Dartmouth , Williams , Bowdoin , Middlebury , and Amherst , all were founded by the Mainline Protestantism , as were later Carleton , Duke ,  Oberlin , Beloit , Pomona , Rollins and Colorado College .
The seven largest U.S. mainline denominations were called by William Hutchison the "Seven Sisters of American Protestantism"  in reference to the major liberal groups during the period between 1900 and 1960.
- United Methodist Church 7,067,162 members (2015) 
- Evangelical Lutheran Church in America 3,563,842 members (2016) 
- Episcopal Church in the United States of America 1,779,335 members (2015) 
- Presbyterian Church (USA) 1,482,767 members (2016) 
- American Baptist Churches in the USA 1,198,046 members (2014) 
- United Church of Christ 914,871 members (2015) 
- Christian Church (Disciples of Christ) 497,423 (2014) 
The Association of Religion Data Archives also considers these denominations to be mainline: 
- Religious Society of Friends (Quakers) 108,500 members
- Reformed Church in America 223,675 members (2015)
- International Council of Community Churches 69,276 members (2009) 
- National Association of Congregational Christian Churches 65,569 members (2000) 
- North American Baptist Conference 47,150 members (2006) 
- Moravian Church in America, Northern Province 24,650 members (2003) 
- Moravian Church in America, Southern Province 21,513 members (1991) 
- Universal Fellowship of Metropolitan Community Churches 15,666 members (2006) 
- Latvian Evangelical Lutheran Church in America 12,000 members (2007)
- Congregational Christian Churches, (not part of any national CCC body)
- Moravian Church in America, Alaska Province
The Association of Religion Data Archives has difficulties collecting data on traditionally African American denominations. Those churches most likely to be identified as mainline include these Methodist groups:
The Catholic Church arrived in what is now the United States during the earliest days of the European colonization of the Americas . At the time the country was founded (meaning the Thirteen Colonies in 1776), only a small fraction of the population there were Catholics (mostly in Maryland ); however, as a result of expansion and immigration over the country's history, the number of adherents has grown dramatically and it is the largest profession of faith in the United States today. With over 67 million registered residents professing the faith in 2008, the United States has the fourth largest Catholic population in the world after Brazil , Mexico , and the Philippines , respectively.
The Church's leadership body in the United States is the United States Conference of Catholic Bishops , made up of the hierarchy of bishops and archbishops of the United States and the U.S. Virgin Islands , although each bishop is independent in his own diocese , answerable only to the Pope .
No primate for Catholics exists in the United States. The Archdiocese of Baltimore has Prerogative of Place , which confers to its archbishop a subset of the leadership responsibilities granted to primates in other countries.
The number of Catholics grew from the early 19th century through immigration and the acquisition of the predominantly Catholic former possessions of France, Spain, and Mexico, followed in the mid-19th century by a rapid influx of Irish , German , Italian and Polish immigrants from Europe, making Catholicism the largest Christian denomination in the United States. This increase was met by widespread prejudice and hostility, often resulting in riots and the burning of churches, convents, and seminaries.  The integration of Catholics into American society was marked by the election of John F. Kennedy as President in 1960. Since then, the percentage of Americans who are Catholic has remained at around 25%. 
According to the Association of Catholic Colleges and Universities in 2011, there are approximately 230 Roman Catholic universities and colleges in the United States with nearly 1 million students and some 65,000 professors.  Catholic schools educate 2.7 million students in the United States, employing 150,000 teachers. In 2002, Catholic health care systems, overseeing 625 hospitals with a combined revenue of 30 billion dollars, comprised the nation's largest group of nonprofit systems. 
Groups of immigrants from several different regions – Eastern Europe , the Mediterranean region , the Middle East , Africa , and India – brought Eastern Orthodoxy and Oriental Orthodoxy to the United States. These branches of Christianity have since spread beyond the boundaries of ethnic immigrant communities and now include multi-ethnic membership and parishes.
Statistically, Eastern Orthodox Christians are among the wealthiest Christians denomination in the United States, and they also tend to be better educated than most other religious groups in America, in the sense that they have a high number of graduate (68%) and post-graduate degrees (28%) per capita.
The Church of Jesus Christ of Latter-day Saints
The Church of Jesus Christ of Latter-day Saints (LDS Church) is a nontrinitarian restorationist denomination. The church is headquartered in Salt Lake City , and is the largest originating from the Latter Day Saint movement which was founded by Joseph Smith in Upstate New York in 1830. It forms the majority in Utah , the plurality in Idaho , and high percentages in Nevada , Arizona , and Wyoming ; in addition to sizable numbers in Colorado , Montana , Washington , Oregon , Alaska , Hawaii and California . Current U.S. membership is 6.4 million. 
In 2010, around 13-14% of Mormons lived in Utah, the center of cultural influence for Mormonism.  Utah Mormons (as well as Mormons living in the Intermountain West ) are on average more culturally and politically conservative and Libertarian than those living in some cosmopolitan centers elsewhere in the U.S.  Utahns self-identifying as Mormon also attend church somewhat more on average than Mormons living in other states. (Nonetheless, whether they live in Utah or elsewhere in the U.S., Mormons tend to be more culturally and politically conservative than members of other U.S. religious groups.)  Utah Mormons often place a greater emphasis on pioneer heritage than international Mormons who generally are not descendants of the Mormon pioneers . 
Christianity was introduced during the period of European colonization . The Spanish and French brought Catholicism to the colonies of New Spain and New France respectively, while British and Germans introduced Protestantism. Among Protestants, adherents to Anglicanism , the Baptist Church , Congregationalism , Presbyterianism , Lutheranism , Quakerism , Mennonite and Moravian Church were the first to settle in the American colonies.
Early Colonial period
Spain established missions and towns in what are now Texas , New Mexico , Arizona , Florida , and California . Many cities and towns still retain in the present day the names of the Catholic saints these missions were named for; an excellent example of this is the full legal name of the city of Los Angeles: El Pueblo de Nuestra Señora Reina de Los Ángeles del Río Porciúncula , or The Town of Our Lady, Queen of the Angels of the Porciuncula River . The city was founded by Franciscan friars, who named their tiny church and later the town that formed around it after the Virgin Mary, also known to Catholics as Our Lady, Queen of the Angels. Similar patterns emerged wherever the Spanish went, such as San Antonio, Texas , (named for Anthony of Padua , Santa Fe, New Mexico (named after Francis of Assisi ,) and Saint Augustine, Florida , (named for Augustine of Hippo ), as was Saint Lucy County and Port Saint Lucy in Florida named for Saint Lucy/Santa Lucia although Saint Petersburg, Florida was not named for St. Peter, but for the city of the same name in Russia.
In the English colonies, Catholicism was introduced with the settling of Maryland .
Conversion of Native Americans to Catholicism was a main goal of the Catholic missionaries, especially the Jesuits. This was common in places where French influence was strong, like Detroit or Louisiana.
Many of the British North American colonies that eventually formed the United States of America were settled in the 17th century by men and women, who, in the face of European religious persecution , refused to compromise passionately-held religious convictions and fled Europe.
The Puritans , a much larger group than the Pilgrims, established the Massachusetts Bay Colony in 1629 with 400 settlers. Puritans were English Protestants who wished to reform and purify the Church of England in the New World of what they considered to be unacceptable residues of Catholicism. Within two years, an additional 2,000 settlers arrived. From 1620 to 1640 Puritans emigrated to New England from England to escape persecution and gain the liberty to worship as they chose independently of the Church of England , England being on the verge of the English Civil War . Most settled in New England, but some went as far as the West Indies . Theologically, the Puritans were "non-separating Congregationalists ." The Puritans created a deeply religious, socially tight-knit and politically innovative culture that is still present in the modern United States. They hoped this new land would serve as a " redeemer nation ."
The Church of England was legally established in the colony in 1619; 22 Anglican clergymen arrived by 1624. In practice, "establishment" meant that local taxes were funneled through the local parish to handle the needs of local government, such as roads and poor relief, in addition to the salary of the minister. There never was a bishop in colonial Virginia; the local vestry consisted of laymen controlled the parish. The colonists were typically inattentive, uninterested, and bored during church services, according to the ministers, who complained that the people were sleeping, whispering, ogling the fashionably dressed women, walking about and coming and going, or at best looking out the windows or staring blankly into space. There were too few ministers for the widely scattered population, so ministers encouraged parishioners to become devout at home, using the Book of Common Prayer for private prayer and devotion (rather than the Bible). The stress on personal piety opened the way for the First Great Awakening , which pulled people away from the established church and into the unauthorized Baptist and Methodist movements.
Tolerance in Rhode Island and Pennsylvania
Roger Williams , who preached religious tolerance, separation of church and state, and a complete break with the Church of England, was banished from Massachusetts and founded Rhode Island Colony , which became a haven for other religious refugees from the Puritan community. Some migrants who came to Colonial America were in search of the freedom to practice forms of Christianity which were prohibited and persecuted in Europe. Since there was no state religion, and since Protestantism had no central authority, religious practice in the colonies became diverse.
The Quakers formed in England in 1652, where they were severely persecuted in England for daring to deviate so far from orthodox Christianity. Many sought refuge in New Jersey, Rhode Island and especially Pennsylvania, which was owned by William Penn , a rich Quaker. The Quakers kept political control until Indian wars broke out; the Quakers were pacifists and gave up control to groups that were eager to fight the Indians.
Beginning in 1683 many German-speaking immigrants arrived in Pennsylvania from the Rhine Valley and Switzerland. Starting in the 1730s Count Zinzendorf and the Moravian Brethren sought to minister to these immigrants while they also began missions among the Native American tribes of New York and Pennsylvania. Heinrich Melchior Muehlenberg organized the first Lutheran Synod in Pennsylvania in the 1740s.
Catholic fortunes fluctuated in Maryland during the rest of the 17th century, as they became an increasingly smaller minority of the population. After the Glorious Revolution of 1689 in England, penal laws deprived Catholics of the right to vote, hold office, educate their children or worship publicly. Until the American Revolution , Catholics in Maryland, like Charles Carroll of Carrollton , were dissenters in their own country but keeping loyal to their convictions. At the time of the Revolution, Catholics formed less than 1% of the population of the thirteen colonies, in 2007, Catholics comprised 24% of US population.
Evangelicalism is difficult to date and to define. Scholars have argued that, as a self-conscious movement, evangelicalism did not arise until the mid-17th century, perhaps not until the Great Awakening itself. The fundamental premise of evangelicalism is the conversion of individuals from a state of sin to a " new birth " through the preaching of the Word. The Great Awakening refers to a northeastern Protestant revival movement that took place in the 1730s and 1740s.
The first generation of New England Puritans required that church members undergo a conversion experience that they could describe publicly. Their successors were not as successful in reaping harvests of redeemed souls. The movement began with Jonathan Edwards , a Massachusetts preacher who sought to return to the Pilgrims' strict Calvinist roots. British preacher George Whitefield and other itinerant preachers continued the movement, traveling across the colonies and preaching in a dramatic and emotional style. Followers of Edwards and other preachers of similar religiosity called themselves the "New Lights," as contrasted with the "Old Lights," who disapproved of their movement. To promote their viewpoints, the two sides established academies and colleges, including Princeton and Williams College . The Great Awakening has been called the first truly American event.
The supporters of the Awakening and its evangelical thrust— Presbyterians , Baptists, and Methodists —became the largest American Protestant denominations by the first decades of the 19th century. By the 1770s, the Baptists were growing rapidly both in the north (where they founded Brown University ), and in the South. Opponents of the Awakening or those split by it—Anglicans, Quakers, and Congregationalists—were left behind.
The First Great Awakening of the 1740s increased religiosity in most of the colonies. By 1780 the percentage of adult colonists who formally held membership in a church was between 10-30%, not counting slaves or Native Americans. North Carolina had the lowest percentage at about 4%, while New Hampshire and South Carolina were tied for the highest, at about 16%. Many others informally associated with the churches.
The Revolution split some denominations, notably the Church of England, most of whose ministers supported the king. The Quakers and some German sects were pacifists and remained neutral. Religious practice suffered in certain places because of the absence of ministers and the destruction of churches, but in other areas, religion flourished.
Badly hurt, the Anglicans reorganized after the war. It became the Protestant Episcopal Church .
In 1794, the Russian Orthodox missionary St. Herman of Alaska arrived on Kodiak island in Alaska and began significantly evangelizing the native peoples. Nearly all the Russians left in 1867 when the U.S. purchased Alaska, but the Orthodox faith remained.
Lambert (2003) has examined the religious affiliations and beliefs of the Founding Fathers of the United States . Of the 55 delegates to the 1787 Constitutional Convention, 49 were Protestants , and two were Catholics (D. Carroll, and Fitzsimons).  Among the Protestant delegates to the Constitutional Convention, 28 were Church of England (or Episcopalian , after the American Revolutionary War was won), eight were Presbyterians , seven were Congregationalists , two were Lutherans , two were Dutch Reformed , and two were Methodists . 
Church and state debate
After independence, the American states were obliged to write constitutions establishing how each would be governed. For three years, from 1778 to 1780, the political energies of Massachusetts were absorbed in drafting a charter of government that the voters would accept. One of the most contentious issues was whether the state would support the church financially. Advocating such a policy were the ministers and most members of the Congregational Church, which received public financial support, during the colonial period. The Baptists tenaciously adhered to their ancient conviction that churches should receive no support from the state. The Constitutional Convention chose to support the church and Article Three authorized a general religious tax to be directed to the church of a taxpayers' choice.
Separation of church and state
In October 1801, members of the Danbury Baptists Associations wrote a letter to the new President-elect Thomas Jefferson . Baptists, being a minority in Connecticut, were still required to pay fees to support the Congregationalist majority. The Baptists found this intolerable. The Baptists, well aware of Jefferson's own unorthodox beliefs, sought him as an ally in making all religious expression a fundamental human right and not a matter of government largesse.
In his January 1, 1802, reply to the Danbury Baptist Association Jefferson summed up the First Amendment's original intent, and used for the first time anywhere a now-familiar phrase in today's political and judicial circles: the amendment established a "wall of separation between church and state." Largely unknown in its day, this phrase has since become a major Constitutional issue. The first time the U.S. Supreme Court cited that phrase from Jefferson was in 1878, 76 years later.
Second Great Awakening
The Second Great Awakening was a Protestant movement that began around 1790, gained momentum by 1800, and after 1820 membership rose rapidly among Baptist and Methodist congregations whose preachers led the movement. It was past its peak by the 1840s. It was a reaction against skepticism, deism , and rational Christianity, and was especially attractive to young women. Millions of new members enrolled in existing evangelical denominations and led to the formation of new denominations. Many converts believed that the Awakening heralded a new millennial age . The Second Great Awakening stimulated the establishment of many reform movements designed to remedy the evils of society before the anticipated Second Coming of Jesus Christ.
During the Second Great Awakening, new Protestant denominations emerged such as Adventism , the Restoration Movement , and groups such as Jehovah's Witnesses and Mormonism . While the First Great Awakening was centered on reviving the spirituality of established congregations, the Second focused on the unchurched and sought to instill in them a deep sense of personal salvation as experienced in revival meetings.
The principal innovation produced by the revivals was the camp meeting . When assembled in a field or at the edge of a forest for a prolonged religious meeting, the participants transformed the site into a camp meeting. Singing and preaching were the main activities for several days. The revivals were often intense and created intense emotions. Some fell away but many if not most became permanent church members. The Methodists and Baptists made them one of the evangelical signatures of the denomination.
African American churches
The Christianity of the black population was grounded in evangelicalism. The Second Great Awakening has been called the "central and defining event in the development of Afro-Christianity." During these revivals Baptists and Methodists converted large numbers of blacks. However, many were disappointed at the treatment they received from their fellow believers and at the backsliding in the commitment to abolish slavery that many white Baptists and Methodists had advocated immediately after the American Revolution.
When their discontent could not be contained, forceful black leaders followed what was becoming an American habit—they formed new denominations. In 1787, Richard Allen and his colleagues in Philadelphia broke away from the Methodist Church and in 1815 founded the African Methodist Episcopal (AME) Church .
After the Civil War, Black Baptists desiring to practice Christianity away from racial discrimination, rapidly set up several separate state Baptist conventions. In 1866, black Baptists of the South and West combined to form the Consolidated American Baptist Convention. This convention eventually collapsed but three national conventions formed in response. In 1895 the three conventions merged to create the National Baptist Convention . It is now the largest African-American religious organization in the United States.
The "secularization of society" is attributed to the time of the Enlightenment . In the United States, religious observance is much higher than in Europe, and the United States' culture leans conservative in comparison to other western nations, in part due to the Christian element.
Liberal Christianity , exemplified by some theologians, sought to bring to churches new critical approaches to the Bible. Sometimes called "liberal theology", liberal Christianity is an umbrella term covering movements and ideas within 19th- and 20th-century Christianity. New attitudes became evident, and the practice of questioning the nearly universally accepted Christian orthodoxy began to come to the forefront.
In the post–World War I era, liberalism was the faster-growing sector of the American church. Liberal wings of denominations were on the rise, and a considerable number of seminaries held and taught from a liberal perspective as well. In the post–World War II era, the trend began to swing back towards the conservative camp in America's seminaries and church structures.
By 1850 Catholics had become the country's largest single denomination. Between 1860 and 1890 the population of Catholics in the United States tripled through immigration; by the end of the decade, it would reach seven million. These huge numbers of immigrant Catholics came from Ireland , Quebec , Southern Germany, Italy, Poland and Eastern Europe . This influx would eventually bring increased political power for the Catholic Church and a greater cultural presence led at the same time to a growing fear of the Catholic "menace." As the 19th century wore on animosity waned, Protestant Americans realized that Catholics were not trying to seize control of the government.
Christian fundamentalism began as a movement in the late 19th century and early 20th century to reject influences of secular humanism and source criticism in modern Christianity. In reaction to liberal Protestant groups that denied doctrines considered fundamental to these conservative groups, they sought to establish tenets necessary to maintaining a Christian identity, the "fundamentals," hence the term fundamentalist.
Over time, the movement divided, with the label Fundamentalist being retained by the smaller and more hard-line group(s). Evangelical has become the main identifier of the groups holding to the movement's moderate and earliest ideas.
In the U.S. and elsewhere in the world, there has been a marked rise in the evangelical wing of Protestant denominations, especially those that are more exclusively evangelical, and a corresponding decline in the mainstream liberal churches.
The 1950s saw a boom in the Evangelical church in America. The post–World War II prosperity experienced in the U.S. also had its effects on the church. Church buildings were erected in large numbers, and the Evangelical church's activities grew along with this expansive physical growth. In the southern U.S., the Evangelicals, represented by leaders such as Billy Graham , have experienced a notable surge displacing the caricature of the pulpit pounding country preachers of fundamentalism. The stereotypes have gradually shifted.
Although the Evangelical community worldwide is diverse, the ties that bind all Evangelicals are still apparent: a "high view" of Scripture, belief in the Deity of Christ, the Trinity, salvation by grace through faith, and the bodily resurrection of Christ.
The Federal Council of Churches, founded in 1908, marked the first major expression of a growing modern ecumenical movement among Christians in the United States. It was active in pressing for reform of public and private policies, particularly as they impacted the lives of those living in poverty, and developed a comprehensive and widely debated Social Creed which served as a humanitarian "bill of rights" for those seeking improvements in American life.
In 1950, the National Council of the Churches of Christ in the USA (usually identified as National Council of Churches , or NCC) represented a dramatic expansion in the development of ecumenical cooperation. It was a merger of the Federal Council of Churches, the International Council of Religious Education, and several other interchurch ministries. Today, the NCC is a joint venture of 35 Christian denominations in the United States with 100,000 local congregations and 45,000,000 adherents. Its member communions include Mainline Protestant , Orthodox , African-American, Evangelical and historic Peace churches. The NCC took a prominent role in the Civil Rights movement and fostered the publication of the widely used Revised Standard Version of the Bible , followed by an updated New Revised Standard Version , the first translation to benefit from the discovery of the Dead Sea Scrolls. The organization is headquartered in New York City, with a public policy office in Washington, DC. The NCC is related fraternally to hundreds of local and regional councils of churches, to other national councils across the globe, and to the World Council of Churches . All of these bodies are independently governed.
Carl McIntire led in organizing the American Council of Christian Churches (ACCC), now with 7 member bodies, in September 1941. It was a more militant and fundamentalist organization set up in opposition to what became the National Council of Churches.
The National Association of Evangelicals for United Action was formed in St. Louis, Missouri on April 7–9, 1942. It soon shortened its name to the National Association of Evangelicals (NEA). There are currently 60 denominations with about 45,000 churches in the organization. The NEA is related fraternally the World Evangelical Fellowship .
In 2006, 39 communions and 7 Christian organizations officially launched Christian Churches Together in the USA (CCT). CCT provides a space that is inclusive of the diversity of Christian traditions in the United States—Evangelical/Pentecostal, Orthodox, Catholic, historic Protestant, and historic Black churches. CCT is characterized by its emphasis on relationships and prayer. Every year these communions and organizations meet over four days to discuss critical social issues, pray and strengthen their relationships. 
Another noteworthy development in 20th-century Christianity was the rise of the modern Pentecostal movement. Pentecostalism , which had its roots in the Pietism and the Holiness movement , many will cite that it arose out of the meetings in 1906 at an urban mission on Azusa Street in Los Angeles, but it actually started in 1900 in Topeka, Kansas with a group led by Charles Parham and the Bethel Bible School < https://en.wikipedia.org/wiki/Charles_Fox_Parham > From there it spread by those who experienced what they believed to be miraculous moves of God there.
Pentecostalism would later birth the Charismatic movement within already established denominations, and it continues to be an important force in Western Christianity.
By the beginning of the 20th century, approximately one-sixth of the population of the United States was Catholic. Modern Catholic immigrants come to the United States from the Philippines , Poland, and Latin America , especially from Mexico. This multiculturalism and diversity have greatly impacted the flavor of Catholicism in the United States. For example, many dioceses serve in both the English language and the Spanish language .
While children and youth in the colonial era were treated as small adults, awareness of their special status and needs grew in the nineteenth century, as one after another the denominations large and small began special programs for their young people. Protestant theologian Horace Bushnell in Christian Nurture (1847) emphasized the necessity of identifying and supporting the religiosity of children and young adults. Beginning in the 1790s the Protestant denominations set up Sunday school programs. They provided a major source of new members. Urban Protestant churchmen set up the interdenominational YMCA (and later the YWCA ) programs in cities from the 1850s. Methodists looked on their youth as potential political activists, providing them with opportunities to engage in social justice movements such as prohibition. Black Protestants, especially after they could form their own separate churches, integrated their young people directly into the larger religious community. Their youth played a major role in the leadership of the Civil Rights movement of the 1950s and the 1960s. White evangelicals in the twentieth century set up Bible clubs for teenagers and experimented with the use of music to attract young people. The Catholics set up an entire network of parochial schools, and by the late nineteenth century probably more than half of their young members were attending elementary schools run by local parishes. Some Missouri Synod German Lutherans and Dutch Reformed churches also set up parochial schools. In the twentieth century, all the denominations sponsored programs such as the Boy Scouts and Girl Scouts.
Demographics by state
Beliefs and attitudes
The Baylor University Institute for Studies of Religion conducted a survey covering various aspects of American religious life.  The researchers analyzing the survey results have categorized the responses into what they call the "four Gods": An authoritarian God (31%), a benevolent God (25%), a distant God (23%), and a critical God (16%).  A major implication to emerge from this survey is that "the type of god people believe in can predict their political and moral attitudes more so than just looking at their religious tradition." 
As far as religious tradition, the survey determined that 33.6% of respondents are evangelical Protestants, while 10.8% had no religious affiliation at all. Out of those without affiliation, 62.9% still indicated that they "believe in God or some higher power". 
Another study, conducted by Christianity Today with Leadership magazine, attempted to understand the range and differences among American Christians. A national attitudinal and behavioral survey found that their beliefs and practices clustered into five distinct segments. Spiritual growth for two large segments of Christians may be occurring in non-traditional ways. Instead of attending church on Sunday mornings, many opt for personal, individual ways to stretch themselves spiritually. 
- 19 percent of American Christians are described by the researchers as Active Christians. They believe salvation comes through Jesus Christ , attend church regularly, are Bible readers, invest in personal faith development through their church, accept leadership positions in their church, and believe they are obligated to "share [their] faith", that is, to evangelize others.
- 20 percent are referred to as Professing Christians. They are also committed to "accepting Christ as Savior and Lord" as the key to being a Christian, but focus more on personal relationships with God and Jesus than on church, Bible reading or evangelizing.
- 16 percent fall into a category named Liturgical Christians. They are predominantly Lutheran , Catholic , Episcopalian , or Orthodox . They are regular churchgoers, have a high level of spiritual activity and recognize the authority of the church.
- 24 percent are considered Private Christians. They own a Bible but don't tend to read it. Only about one-third attend church at all. They believe in God and in doing good things, but not necessarily within a church context. This was the largest and youngest segment. Almost none are church leaders.
- 21 percent in the research are called Cultural Christians . These do not view Jesus as essential to salvation. They exhibit little outward religious behavior or attitudes. They favor a universality theology that sees many ways to God. Yet, they clearly consider themselves to be Christians.
Gallup International indicates that 41%  of American citizens report they regularly attend religious services , compared to 15% of French citizens , 10% of UK citizens ,  and 7.5% of Australian citizens . 
Church attendance varies significantly by state and region. In a 2014 Gallup survey, less than half of Americans said that they attended church or synagogue weekly. The figures ranged from 51% in Utah to 17% in Vermont . 
The most methodologically rigorous study of Hispanic and Latino Americans religious affiliation to date was the (HCAPL) National Survey, conducted between August and October 2000. This survey found that 70% of all Hispanic and Latino Americans are Catholic, 20% are Protestant, 3% are "alternative Christians" (such as Mormon or Jehovah's Witnesses ). 
The majority of African Americans are Protestant (78%), many of whom follow the historically black churches.  A 2012 Pew Research Center study found that 42% of the Asian Americans identify themselves as Christians . 
Beginning in the 16th century, the Spanish (and later the French and English) introduced Catholicism. From the 19th century to the present, Catholics came to the US in large numbers due to the immigration of Italians , Hispanics, Portuguese , French , Polish , Irish , Highland Scots, Dutch, Flemish, Hungarians , Germans , Lebanese ( Maronite ), and other ethnic groups.
Most of the Eastern Orthodox adherents in the United States are descended from immigrants of Eastern European or Middle Eastern background, especially from Greek , Russian , Ukrainian , Arab , Bulgarian , Romanian , or Serb backgrounds.  
Data from the Pew Research Center show that as of 2013, there were about 1.6 million Christians from Jewish background, most of them Protestant .    According to the same data, most of the Christians of Jewish descent were raised as Jews or are Jews by ancestry. 
A study from 2015 estimated some 450,000 American Muslims who had converted to Christianity , most of whom belong to an evangelical or Pentecostal community.  In 2010 there were approximately 180,000 Arab-Americans and about 130,000 Iranian Americans who converted from Islam to Christianity. Dudley Woodbury, a Fulbright scholar of Islam, estimates that 20,000 Muslims convert to Christianity annually in the United States . 
It's been also reported that conversion into Christianity is significantly increasing among Korean Americans ,  Chinese Americans ,  and Japanese Americans .  By 2012, the percentage of Christians within the mentioned communities was 71%,  more than 30%  and 37%. 
Messianic Judaism (or Messianic Movement) is the name of a Christian movement comprising a number of streams, whose members may consider themselves Jewish.  It blends elements of religious Jewish practice with evangelical Christianity. Messianic Judaism affirms Christian creeds such as the messiahship and divinity of " Yeshua " (the Hebrew name of Jesus) and the Triune Nature of God, while also adhering to some Jewish dietary laws and customs. As of 2012, population estimates for the United States were between 175,000 and 250,000 members.