The apportionment of seats in the House of Representatives was based on the 1850 United States census.

The Senate had a Democratic majority, and the House was controlled by a coalition of Representatives led by Nathaniel P. Banks, a member of the American Party.

During the elections for this Congress, opponents to the Democrats used the Whig party label inconsistently and not at all in some states.

Senators were elected by the state legislatures every two years, with one-third beginning new six-year terms with each Congress.

Preceding the names in the list below are Senate class numbers, which indicate the cycle of their election.