The Old Stone House is the oldest unchanged building in Washington, D.C. , United States . The house is also Washington's last Pre- Revolutionary Colonial building on its original foundation. Built in 1765, Old Stone House is located at 3051 M Street , Northwest in the Georgetown neighborhood. Unlike many Colonial homes in the area, sentimental local folklore preserved the Old Stone House from being demolished.
The Old Stone House was constructed in three phases during the 18th century and is an example of vernacular architecture . During its history, the house was started as a one-story building and gradually became a used car dealership later. After a renovation by the National Park Service (NPS) in the 1950s, the Old Stone House was turned into a house museum . The Old Stone House stands among the neighborhood's stores and restaurants as an example of local history for tourists, shoppers, and students. The building is part of the Rock Creek Parkway urban natural area and was listed on the National Register of Historic Places in 1973. The Old Stone House is also a contributing property to the Georgetown Historic District, a National Historic Landmark . Today, the home is 85% original to its 18th-century construction.
In 1764, Christopher and Rachel Layman bought Lot Three, a piece of land in Georgetown's commercial district. They paid £1 10s. and financed the construction of a simple one-room house the following year. The lot faced Bridge Street, now known as M Street , NW. The Laymans' only possessions were Christopher's tools, a stove, Bibles, and some furniture. When Christopher died unexpectedly in 1765, Rachel remarried two years later and sold the house to another widow, Cassandra Chew. 
Chew was a member of the upper-middle class and owned several properties in and around Georgetown. Because of her wealth, Chew was able to finance the construction of a rear kitchen in 1767 and a second floor between 1767 and 1775. The third floor originated in a property line dispute during the 1790s: the original west wall had been constructed six feet (2 m) beyond the property line and had to be dismantled. Chew used the opportunity to add the upper floor and was completed by 1790. 
Following the American Revolutionary War , government officials had carved out land from Virginia and Maryland to use as the new nation's capital. Pierre Charles L'Enfant , appointed by President George Washington to design the city layout, arrived in Georgetown on March 9, 1791, and began his work. Washington and L'Enfant held their meetings at Suter's Tavern , a former building owned by John Suter near 31st and K Streets, NW.  At the time, John Suter Jr. was renting a room at the Old Stone House and for many years, locals believed that Washington and L'Enfant had actually met at the Old Stone House instead. This folklore is the reason the house was never demolished, and for many years a sign hung over the front door which said, "George Washington's Headquarters." After some research done by the National Park Service, they found out that the folklore was not true. By the time they had found that out, they already owned the House and the property. 
When Chew died in 1807, she bequeathed Old Stone House to one of her daughters, Mary Smith Brumley, who became the first of many owners who operated businesses out of the house. Like her mother, Brumley was a businesswoman and ran a successful merchant's shop inside the home. The house, then known as the Layman home, remained in the family until 1875.  
Over the years, the house had been used as a shop for hats, tailors, locksmiths, clockmakers, house roofers and house painters. The Old Stone House was still privately owned in 1953 – serving as used car dealership that used the back yard as a parking lot – when the Federal government purchased the property for $90,000 ($805,600 today) and turned it over to the National Park Service. Between 1953 and 1960 the NPS removed the majority of 19th and 20th century intrusions to the home and the parking lot was turned into an English garden . 
After the renovation, the Old Stone House was opened to the public in 1960. It became a part of the George Washington Memorial Parkway , but stewardship of the house was later transferred to the Chesapeake and Ohio Canal National Historical Park . In the late 1980s, stewardship of the Old Stone House was once again transferred, this time to the Rock Creek Park . 
Old Stone House is an example of vernacular architecture . The exterior of the house, constructed of blue granite and fieldstone , was quarried from a location two miles (3 km) away near the Potomac River .  The walls range from two to three feet (60-90 cm) thick. The oak used in the house was harvested from forests that were once predominant in Georgetown. 
On the first floor, the original roof and front door were constructed of solid oak and cut with a pit saw. Marks left by the large saw can be seen on the first floor. The kitchen walls and fireplace contain irregular stones that were stacked and affixed with a mortar consisting of sand, lime, ash, and water. The kitchen's hearth is large enough to heat the entire house. 
The second floor architecture differs significantly from the first floor since Chew was able to afford higher quality building material. A second doorway and staircase were constructed for family members and guests. The original entrance was then reserved for workmen and deliveries. There are three rooms located on this floor, the dining room, a bedroom, and the parlor. The hallway between the dining room and two front rooms features a high ceiling for ventilation in Georgetown's hot summers. The second floor walls were plastered and painted. Chair rails were added to prevent damage to the walls. In the dining room, a dumbwaiter concealed by recessed pine cabinetry delivered food from the kitchen below. A clock believed to have been made by John Suter Jr., located in the dining room, is the only original piece of furniture left in the house. The clock dates back to the early 19th century. The bedroom features a carved wooden mantle that is believed to be of French origin. 
The third floor, constructed of brick, was a private space. It was completed around 1790. It is much plainer than the second floor, with unfinished paneling and unpainted walls. There are three rooms on this floor, believed to be children's bedrooms and a storage area. A closet is attached to the third-floor bedroom, an unusual feature in 18th-century colonial houses. Closets were considered to be rooms by the British monarchy and therefore were subject to a "closet tax".  Due to it being built after the Revolutionary War, the Old Stone House's closet was not subject to the tax.
The Colonial Revival garden , located behind the house and bordered by a white picket fence, is 399 feet (122 m) deep and 76 feet (23 m) wide.  Roses, perennials , and bulbs are located throughout the garden.
Visitors are greeted by Park Rangers who tell the history of one of the oldest structures in Washington DC.  The kitchen, parlor and bedrooms, furnished as they would have been in the late 18th century, are open for viewing. A gift shop operated by Eastern National is located inside the front room of the house. The garden is used for simple wedding ceremonies and as an area for locals and tourists to rest while shopping or to enjoy a lunch break. The building is open to the public seven days a week, from 11:00am to 6:00pm (eastern time) and the garden is open every day from dawn until dusk.