Stop 3: Finding D.C.’s Foundation

Pierre L’Enfant designed the avenues of Washington, DC to connect and radiate from its two most important buildings: The White House and the U.S. Capitol. Construction began on the White House in 1792 and the Capitol in 1793. Like most old buildings in cities, these two buildings were constructed with materials that were gathered close to the city itself.

Hard, metamorphic rock from the Sykesville Formation was quarried from Little Falls, Maryland to be used in the foundations of each building. Softer, sedimentary rock called Aquia Creek sandstone was quarried from Virginia for the rest of the buildings.

It is fitting that the two buildings that form the basis of the city’s design be made from local rock, because it is this rock that supports the city. And without the White House and the Capitol, how would the United States government support itself?


The White House

Construction began in 1792, and by 1800 the Second President, John Adams, and his wife Abigail were ready to move into the “President’s House.” It was also known as the "President's Palace" and the "Executive Mansion" until President Theodore Roosevelt officially named it the “White House” in 1901. The porous sandstone, which is naturally a tan color, has been whitewashed since construction in the 1790s, and painted white ever since the “President’s House” was burned by the British in the War of 1812.

The White House has not only been renamed, it has also been expanded and repaired. Some repairs involved the Aquia Creek sandstone. This stone, used on the outside walls, was easily carved into decorative pieces like columns and windows. Unfortunately, it was also soft enough to wear away when it was exposed to the weather. Between 1980 and 1992, two centuries of whitewash and paint were removed to reveal that some White House sandstone blocks had to be completely replaced. Visit The White House online.


The United States Capitol

The Capitol is the building where Senators and Representatives meet to make laws. As the country grew, and more states sent representatives to the Capitol, the building had to grow as well. The Capitol has many construction and repair stories and is made of many different materials; one unusual story stars the Aquia Creek sandstone. As the Capitol expanded, the original wood and copper dome looked too small, so a larger cast iron dome, painted white, was constructed. Because of that renovation, the original sandstone columns under the dome were replaced with larger and sturdier marble columns.

What do you think happened to the old Capitol columns? Today, instead of holding up the dome of the Capitol, the Aquia Creek sandstone columns hold up the blue sky at the National Arboretum. Visit the US Capitol online.


Continue Your Tour of the National Mall

Stop 1: The Geology of the Washington D.C. Area

Stop 2: The History of Washington D.C.

Stop 3: Finding D.C.’s Foundation

Stop 4: A Watery Past

Stop 5: GeoStory of the Lincoln Memorial

Stop 6: Remembering War

Stop 7: Stories in Stone at the Franklin Delano Roosevelt Memorial

Stop 8: Thomas Jefferson Memorial - A Place of Controversy

Stop 9: Washington Monument - The Nation’s Most Unique Rock Collection

Stop 10: Who Cares for the National Mall







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