The House of Representatives
The Constitution requires a census to be taken every 10 years. If a state's population increases, that state's number of representatives can increase too. There were 59 members at the first session of the House of Representatives. Today there are 435 members, divided among the 50 states in proportion to their total population. In addition, there are 6 non-voting members, representing the District of Columbia, the Commonwealth of Puerto Rico, and four other territories of the United States.
Members of the House are elected every two years and must be 25 years of age, a U.S. citizen for at least seven years, and a resident of the state (but not necessarily the district) they represent.
The House has several powers assigned exclusively to it, including the power to initiate revenue bills, impeach federal officials, and elect the President in the case of an Electoral College tie.