resigned April 20, 1818.New member elected Between April and November 1818.Democratic-Republican hold.Successor seated November 16, 1818.Successor also elected to the next term, see below. | nowrap | |- ! | Thomas B. Robertson | | Democratic-Republican | 1812 | | Incumbent resigned April 20, 1818.New member elected July 6–8, 1818.Democratic-Republican hold.Successor seated November 16, 1818.Successor elected the same day to the next term, see below. | nowrap | |- ! | Samuel D. Ingham | | Democratic-Republican | 1818 | | Incumbent resigned July 6, 1818.New member elected October 13, 1818.Democratic-Republican hold.Successor also elected the same day to the next term, see below.Successor seated November 16, 1818. | nowrap | |- ! | Daniel Forney | | Democratic-Republican | 1815 | | Incumbent resigned sometime in 1818.New member elected November 7, 1818.Federalist gain.Successor seated December 2, 1818.Successor later re-elected, see below. | nowrap | |- ! | Peterson Goodwyn | | Democratic-Republican | 1803 | | Incumbent died February 21, 1818.New member elected November 16, 1818.Democratic-Republican hold.Successor seated April 21, 1818.Successor later lost re-election, see below. | nowrap | |- ! | John Forsyth | | Democratic-Republican | 1812 | | Incumbent resigned November 23, 1818 when elected U.S. Senator.New member elected January 4, 1819 both to finish the term and to the next term.Democratic-Republican hold.Successor seated February 18, 1819. | nowrap | |- ! | George Mumford | | Democratic-Republican | 1817 | | Incumbent died December 31, 1818.New member elected between January 1, 1819 and February 11, 1819.Democratic-Republican gain.Successor seated February 11, 1819.Successor was later re-elected to the next term, see below. | nowrap | |} 16th Congress |- | colspan=6 | |} Alabama |- ! | colspan=3 | New seat | | Alabama was admitted as a state December 14, 1819.Incumbent territorial delegate re-elected as member.Democratic-Republican gain.New member seated December 14, 1819. | nowrap | |} Alabama Territory See Non-voting delegates, below. Arkansas Territory See Non-voting delegates, below. Connecticut Connecticut elected its members September 21, 1818. The delegation changed from seven Federalists to seven Democratic-Republicans then the retirement of six incumbents and the party-change of the seventh. |- ! rowspan=7 | | Ebenezer Huntington | | Federalist | 1817 | | Incumbent retired.New member elected.Democratic-Republican gain. | rowspan=7 nowrap | |- | Jonathan O. Moseley | | Federalist | 1804 | | Incumbent changed parties and re-elected.Democratic-Republican gain. |- | Samuel B. Sherwood | | Federalist |