The federal government of the United States is the central United States governmental body, established by the United States Constitution. The federal government has three branches: the legislative, executive, and judiciary. Through a system of separation of powers and the system of "checks and balances," each of these branches has some authority to act on its own, some authority to regulate the other two branches, and has some of its own authority, in turn, regulated by the other branches. The policies of the federal government have a broad impact on both the domestic and foreign affairs of the United States. In addition, the powers of the federal government as a whole are limited by the Constitution, which, per the Tenth Amendment, gives all power not directed to the National government, to the State level.

The seat of the federal government is in the federal district of Washington, D.C.

Legislative branch

main: United States Congress The United States Congress is the legislative branch of the federal government. It is bicameral, comprising the House of Representatives and the Senate. The House of Representatives consists of 435 voting members, each of whom represents a congressional district and serves for a two-year term. In addition to the 435 voting members there are five non-voting members, consisting of four delegates and one resident commissioner. There is one delegate each from the District of Columbia, Guam, Virgin Islands, and American Samoa, and the resident commissioner is from Puerto Rico. House seats are apportioned among the states by population; in contrast, each state has two Senators, regardless of population. There are a total of 100 senators (as there are currently 50 states), who serve six-year terms (one third of the Senate stands for election every two years). Each congressional chamber (House or Senate) has particular exclusive powers—the Senate must give "advice and consent" to many important Presidential appointments, and the House must introduce any bills for the purpose of raising revenue. However, the consent of both chambers is required to make any law. The powers of Congress are limited to those enumerated in the Constitution; all other powers are reserved to the states and the people. The Constitution also includes the "necessary-and-proper clause", which grants Congress the power to "make all laws which shall be necessary and proper for carrying into execution the foregoing powers." Members of the House and Senate are elected by first-past-the-post voting in every state except Louisiana and Washington, which have runoffs.

The Constitution does not specifically call for the establishment of Congressional committees. As the nation grew, however, so did the need for investigating pending legislation more thoroughly. The 108th Congress (2003-2005) had 19 standing committees in the House and 17 in the Senate, plus four joint permanent committees with members from both houses overseeing the Library of Congress, printing, taxation, and the economy. In addition, each house can name special, or select, committees to study specific problems. Because of an increase in workload, the standing committees have also spawned some 150 subcommittees.