Before a person can serve in Congress, they must meet a set of constitutional requirements. To serve in the House of Representatives, a person must be at least 25 years old, a U.S. citizen for at least seven years, and an inhabitant of the state they represent. The Senate sets a higher bar: senators must be at least 30 years old, a U.S. citizen for at least nine years, and an inhabitant of the state they represent. Neither chamber requires members to live in the specific district they represent, only in the state.
These qualifications were deliberately modest. The founders wanted Congress, particularly the House, to remain accessible to ordinary citizens. As James Madison wrote in Federalist 52, the door to the House "is open to merit of every description, whether native or adoptive, whether young or old." The citizenship requirements were designed to balance two concerns: preventing foreign interference in American politics while not discouraging immigration or shutting naturalized citizens out of government entirely.
Once those qualifications are met, members must win a general or midterm election to take office. House members are elected every two years and represent specific congressional districts, with the number of seats per state determined by population. Senators serve six-year terms and are elected statewide, with each state receiving exactly two regardless of population. Originally, senators were chosen by state legislatures, but the 17th Amendment, ratified in 1913, established the direct election of senators by voters after concerns about corruption and special interests influencing state legislatures made reform unavoidable. If a seat becomes vacant before a term ends, House vacancies are filled through special elections, while most Senate vacancies are filled by a temporary gubernatorial appointment until an election can be held.