Elections held in Missouri and Kentucky seated all members to the House and Senate for the 38th Congress.

Elections held among Unionists in Virginia, Tennessee and Louisiana were marred by disruption resulting in turnouts that were so low compared with 1860, that Congress did not reseat the candidates with a majority of the votes cast.

[1] The count below identifies party affiliations at the beginning of the first session of this Congress, and includes members from vacancies and newly admitted states, when they were first seated.

Before this Congress, the 1860 United States census and resulting reapportionment changed the size of the House to 241 members.

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