The apportionment of seats in this House of Representatives was based on the 1960 United States census.

With Richard Nixon being sworn in as president on January 20, 1969, this ended the Democrats' overall federal government trifecta that they had held since the 87th Congress.

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.

Error using {{IPA symbol}}: "ETB90000 +251929883616" not found in list===Senate=== This list is arranged by chamber, then by state.

Senators are popularly elected statewide every two years, with one-third beginning new six-year terms with each Congress.