States are represented in the House of Representatives in approximate proportion to their populations, with every state guaranteed at least one seat. There are currently 435 voting representatives. Five delegates and one resident commissioner serve as non-voting members of the House, although they can vote in committee. Representatives must be 25 years old and must have been U.S. citizens for at least 7 years. Representatives serve 2-year terms.
Read up on the relationship between the two chambers with these essays by the Senate Historian's Office.
Retirement Benefits for Members of Congress (CRS) (pdf)
Biographical Directory of the U.S. Congress, 1774-Present (bioguide.congres.gov)
Pictorial Directory (105th Congress-115th Congress) (GPO-govInfo)
Link to tables of information on the history of the House of Representatives.
History of the House (history.house.gov)
Party Division of the House of Representatives, 1789-present (history.house.gov)