In March 1820, seven House seats transferred from Massachusetts to Maine after the latter seceded from the former to become a separate state.

The size of the House then increased to 187 seats after Missouri achieved statehood in 1821.

The virtually nonpartisan Era of Good Feelings, a period of national political dominance by the Democratic-Republican Party, continued.

Despite small gains, the Federalist Party remained relegated to limited state and local influence.

Alabama elected its member August 5–6, 1821, after the term began but before the new Congress convened.

Connecticut elected its members April 2, 1821, after the term began but before the new Congress convened.

And, in fact, additional ballots were held on January 22, 1821, and September 10, 1821, after the term began but before the new Congress convened.

New York elected its members April 24–26, 1821, after the term began but before the new Congress convened.

In a few cases, marked as "Clintonian/Federalist" below, it is unclear whether a candidate on the joint ticket was Democratic-Republican or Federalist.

North Carolina elected its members August 9, 1821, after the term began but before the new Congress convened.

Tennessee elected its members August 9–10, 1821, after the term began but before the new Congress convened.

The additional ballots were held December 11, 1820, and February 19, May 1, July 2, September 4, and October 22, 1821.

Virginia elected its members in April 1821, after the term began but before the new Congress convened.