The United States Congress passes twelve amendments to the United States Constitution: The Congressional Apportionment Amendment (which was never ratified), the Congressional Compensation Amendment, and the ten that are known as the Bill of Rights.

The Twenty-seventh Amendment (Amendment XXVII, also known as the Congressional Compensation Act of 1789) to the United States Constitution prohibits any law that increases or decreases the salary of members of Congress from taking effect until after the next election of the House of Representatives has occurred. It is the most recently adopted amendment but was one of the first proposed.

The 1st Congress submitted the amendment to the states for ratification on September 25, 1789, along with 11 other proposed amendments (Articles IXII). The last ten Articles were ratified in 1791 to become the Bill of Rights, but the first two, the Twenty-seventh Amendment and the proposed Congressional Apportionment Amendment, were not ratified by enough states to come into force with them.

The proposed congressional pay amendment was largely forgotten until 1982, when Gregory Watson, a 19-year-old sophomore at the University of Texas at Austin, wrote a paper for a government class in which he claimed that the amendment could still be ratified. He later launched a nationwide campaign to complete its ratification. The amendment eventually became part of the United States Constitution, effective May 5, 1992, completing a record-setting ratification period of 202 years, 7 months, and 10 days, beating the previous record set by the Twenty-second Amendment of 3 years and 343 days.The idea behind this amendment is to reduce corruption in the legislative branch by requiring an election before a congressperson's salary increase takes effect. The public can thus remove members of Congress from office before their salaries increase.

The United States Congress is the legislature of the federal government of the United States. It is bicameral, being composed of a lower body, the House of Representatives, and an upper body, the Senate. The Congress meets in the United States Capitol in Washington, D.C. Both 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 vice president of the United States has a vote in the Senate only when senators are evenly divided. The House of Representatives has six non-voting members.The sitting of a Congress is for a two-year term, at present, beginning every other January. Elections are held every even-numbered year on Election Day. The members of the House of Representatives are elected for the two-year term of a Congress. The Reapportionment Act of 1929 establishes that they be elected in single-member constituencies or districts by first-past-the-post and that Congressional districts be apportioned to states by population every ten years using the United States Census results, provided that each state has at least one Congressional representative. Each senator is elected at-large in their state for a six-year term, with terms staggered, so every two years approximately one-third of the Senate is up for election. Each state, regardless of population or size, has two senators, so currently, there are 100 senators for the 50 states.

Article One of the United States Constitution requires that members of Congress must be at least 25 years old (House) or at least 30 years old (Senate), have been a citizen of the United States for seven (House) or nine (Senate) years, and be an inhabitant of the state which they represent. Members in both chambers may stand for re-election an unlimited number of times.

The Congress was created by the Constitution of the United States and first met in 1789, replacing in its legislative function the Congress of the Confederation. Although not legally mandated, in practice since the 19th century, Congress members are typically affiliated with one of the two major parties, the Democratic Party or the Republican Party, and only rarely with a third party or independents affiliated with no party. In the case of the latter, the lack of affiliation with a political party does not mean that such members are unable to caucus with members of the political parties. Members can also switch parties at any time, although this is quite uncommon.