United States senators

More than 2,000 people have served in the U.S. Senate since its establishment in 1789. Senators are charged with the important tasks of making laws, ratifying treaties, approving public appointments of high-ranking officials within the U.S. government, and adjudicating impeachment proceedings. The number of senators throughout U.S. history is several times smaller than the number of officials who have served in the U.S. House of Representatives (which stands at more than 11,000), because the Senate is the smaller house of the national legislature (Congress of the United States). The Senate is made up of 100 members; two members are elected from each of the 50 U.S. states, and each senator serves a six-year term.

Ten members have had careers in the Senate that have lasted 40 years or more. Of these, seven have carried their tenure into the 21st century. Robert C. Byrd of West Virginia (whose tenure lasted more than 51 years, from January 3, 1959, to June 28, 2010) is the longest-serving member in U.S. Senate history, followed by Daniel K. Inouye of Hawaii (who served nearly 50 years, from January 3, 1963, to December 17, 2012) and Patrick J. Leahy from Vermont (who served 48 years, from January 3, 1975, to January 3, 2023). The longest-serving member still in the Senate is Chuck Grassley of Iowa, who began his service on January 3, 1981. Senators serving in the 118th Congress are listed in the table below.