The United States Capitol, often called the Capitol or the Capitol Building, is the seat of the United States Congress, the legislative branch of the federal government. It is located on Capitol Hill at the eastern end of the National Mall in Washington, D.C. Although no longer at the geographic center of the national capital, the U.S. Capitol forms the origin point for the street-numbering system of the district as well as its four quadrants.

The United States Congress is the legislature of the federal government of the United States. It is bicameral, composed of a lower body, the House of Representatives, and an upper body, the Senate. It meets in the U.S. Capitol in Washington, D.C. Senators and representatives are chosen through direct election, though vacancies in the Senate may be filled by a governor's appointment. Congress has 535 voting members: 100 senators and 435 representatives. The U.S. vice president has a vote in the Senate only when senators are evenly divided. The House of Representatives has six non-voting members.