George Washington didn't sleep here.
We have to start there, because for many years the idea that he had was the Old Stone House's biggest claim to fame, and is the main reason it's still standing.
The story grew from a series of meetings in 1791 between Washington and Pierre L'Enfant, who had been hired to lay out the new city. They stayed and met at Suter's Tavern, owned by John Suter. Suter's son, John Jr., was a renter at the Stone House. Over a number of years a confusion grew over the two Suters, and in the 19th century, a sign appeared over the door proclaiming it "George Washington's Headquarters."
While that likely saved it from demolition, it didn't guarantee much respect. Over the years it was used as commercial premises by hatters, tailors, locksmiths, clockmakers, roofers, painters, and finally a used car dealership that used the adjoining gardens as a parking lot.
The house passed through numbers of owners over the years, and was finally bought in 1951—for only $90,000—by the National Park Service. After renovations to remove the 19th and 20th centuries from the building and to turn the parking lot into an English-style garden, it opened to visitors in 1960.
The house itself is now the oldest house in the District. It started as a simple one-room one-floor house in 1764. When a wealthier owner bought it three years later, she added a kitchen, and later a second floor.
The third floor resulted from a property dispute. Turns out that the back wall of the original building extended six feet over the property line. While rebuilding the back wall, the third floor was added.
The walls are thick. It really is, literally, a stone house, built of granite and fieldstone from a nearby quarry, with walls two to three feet thick. The thick oak floors also came from local sources.