Following the congressional reapportionment based on the 1820 United States census, the House increased by 26 seats to a total of 213.

This was the last House election during the virtually nonpartisan Era of Good Feelings and the largest midterm gain of seats by a President's party.

Representatives elected to the 18th Congress are often classified by how they voted in the 1825 contingent election, which after a controversial, unanticipated political deal chose John Quincy Adams President, triggering a new, rancorous, abruptly realigned period of partisanship.

Alabama elected its members August 3, 1823, after the term began but before the new Congress convened.

Delaware was reduced once more from two back to one seat after the fourth census, which number has remained constant to the present day.

Indiana gained two seats in reapportionment following the 1820 United States census, and elected its members August 5, 1822.

Although Maine neither gained nor lost seats after the 1820 United States census, redistricting placed two incumbents into the 3rd district.

Maine elected its members April 7, 1823, after the term began but before the new Congress convened.

Only five candidates received the requisite majority, and so a May 11, 1823, run-off election was held for the sixth seat.

As in the previous election, the Democratic-Republican Party in New York was divided into two factions, the "Bucktails" and the Clintonians, which distinction is not marked here.

North Carolina's delegation remained unchanged after the census, at thirteen seats.

North Carolina elected its members August 14, 1823, after the term began but before the new Congress convened.

Tennessee elected its members August 7–8, 1823, after the term began but before the new Congress convened.

This would be the last year that Vermont would use an at-large district until 1932, when its representation was reduced to a single seat.