The United States Capitol utilized slave labor in its construction.

Here's a commemorative marker from the Architect of the Capitol recognizing the role slaves played in building the nation's "Temple of Liberty".

Slaves helped build Jefferson's mansion of Monticello: http://www.monticello.org/site/house-and-gardens/monticello-house-faq Slaves helped build the White House http://www.whitehousehistory.org/history/white-house-timelines/african-americans-1790s-1840s.html Slave labor built many plantation homes that still stand today. Slaves likely built the first Smithsonian Museum building in Washington, as this investigation shows: http://www.southernspaces.org/2012/enslaved-labor-and-building-smithsonian-reading-stones Slaves likely helped to build Washington's family home of Mount Vernon. A slave, Paul Jennings, also was likely the person who saved the famous Gilbert Stuart portrait of George Washington, when the White House was burned during the War of 1812.

Basically, slaves were the main labor for a large percentage of buildings in slave states. Typically, they were hired as construction crew during down times when they weren't needed for farming purposes, and their owners were paid for their use. You can read first hand about this practice in the book 12 Years a Slave, which was the basis for the movie of the same name. The author was a skilled carpenter before being kidnapped into slavery, so when he became a slave, his owners would rent him out (and other slaves too) to carpenters to build things, either during the off season, or when the owner needed funds due to debt. As hired labor, they were still slaves and their master received their "wages". The carpenter was their overseer during that time and was free to whip them and punish them in other ways. Some slaves specialized in carpentry, and that was their main job all year round, though typically it was a non-slave who was the master carpenter who oversaw the building.

The White House was built using slave labor (at least in part), as were many of the extant buildings at Monticello. Some colleges/universities were built with slave labor, including the University of South Carolina, and the University of North Carolina at Chapel Hill. Slave labor was also used in the construction of many of the early railroads in South Carolina, which is mentioned (barely) in this article. However, if I recall correctly, "Down by the Riverside" by Charles Joyner may touch on it in more detail.

Montgomery Bell had slaves dig a tunnel on the Harpeth River outside Nashville, TN, in order to power an iron forge. Pretty impressive and still there.

At least some of the construction of the US Capitol was carried out by slaves was carried out by slaves, they being the easiest labor to obtain in a largely rural area. In addition, I know slaves helped build a number of southern railroads, such as the North Carolina Railroad, which are still in operation today (though, of course, the tracks and right-of-way have been vastly improved).

The old Cornwall Iron Furnace in Pennsylvania used to be the largest slave-owning enterprise in the state. One of the few places the US could get cannons without having to seize a British fort. The same enterprise employed slave labor to produce gunpowder, and at one point innovated by purchasing German prisoners of war as indentured servants to engage in such activities.

Brown University has a building or two that slaves played a part in constructing. The Brown family for whom the school is named was one of the most successful slaving families in the country.

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