The U.S. Congress is the legislative branch and a core institution of the United States federal government, established by Article I of the U.S. Constitution. It is a bicameral legislature, meaning it consists of two chambers: the House of Representatives and the Senate. The institution first organized in 1789, following the ratification of the Constitution in 1788. It was created to replace the weak central government under the Articles of Confederation, which lacked a credible national authority. The bicameral structure was a compromise to balance representation based on population (House) with equal representation for each state (Senate).
Congress's primary function is to enact federal law. The House has 435 voting members, elected for two-year terms, while the Senate has 100 members (two from each state), serving six-year terms. Article I, Section 8 enumerates its powers, including the authority to regulate commerce, declare war, and raise armed forces. A bill must pass both the House and the Senate before being sent to the President, whose veto can be overridden by a two-thirds majority in both chambers. The House holds the exclusive power to originate revenue bills and impeach federal officials, while the Senate has the sole power to try impeachments, ratify treaties, and confirm executive and judicial appointments.
Congress is central to the U.S. system of separation of powers and checks and balances, acting as a check on the Executive and Judicial branches. A significant change occurred with the 17th Amendment in 1913, which mandated the direct popular election of Senators, replacing their selection by state legislatures. Recently, Congress has reasserted its authority over the executive branch bureaucracy, notably through the use of the Congressional Review Act (CRA) to overturn agency rules.