| | Incumbent died April 24, 1857.New member elected October 13, 1857.Democratic hold. | nowrap | |} Alabama |- ! | Percy Walker | | Know Nothing | 1855 | | Incumbent retired.New member elected.Democratic gain. | nowrap | |- ! | Eli Sims Shorter | | Democratic | 1855 | Incumbent re-elected. | nowrap | |- ! | James Ferguson Dowdell | | Democratic | 1853 | Incumbent re-elected. | nowrap | |- ! | William Russell Smith | | Know Nothing | 1851 | | Incumbent lost re-election.New member elected.Democratic gain. | nowrap | |- ! | George S. Houston | | Democratic | 18411849 1851 | Incumbent re-elected. | nowrap | |- ! | Williamson Robert Winfield Cobb | | Democratic | 1847 | Incumbent re-elected. | nowrap | |- ! | Sampson Willis Harris | | Democratic | 1847 | | Incumbent retired.New member elected.Democratic hold. | nowrap | |} Arkansas |- ! | Alfred B. Greenwood | | Democratic | 1853 | Incumbent re-elected. | nowrap | |- ! | Albert Rust | | Democratic | 1854 | | Incumbent lost renomination.New member elected.Democratic hold. | nowrap | |} California |- ! rowspan=2 | | James W. Denver | | Democratic | 1854 | | Incumbent retired.New member elected.Democratic hold. | rowspan=2 nowrap | |- | Philemon T. Herbert | | Democratic | 1854 | | Incumbent retired after manslaughter acquittal.New member elected.Democratic hold. |} Connecticut |- ! | Ezra Clark Jr. | | Know Nothing | 1855 | | Incumbent re-elected to a new party.Republican gain. | nowrap | |- ! | John Woodruff | | Know Nothing | 1855 | | Incumbent lost re-election.New member elected.Democratic gain. | nowrap | |- ! | Sidney Dean | | Know Nothing | 1855 | | Incumbent re-elected to a new party.Republican gain. | nowrap | |- ! | William W. Welch | | Know Nothing | 1855 | | Incumbent retired.New member elected.Democratic gain. | nowrap | |} Delaware |- ! | Elisha D. Cullen | | Know Nothing | 1854 | | Incumbent lost re-election.New member elected.Democratic gain. | nowrap | |} Florida |- ! | Augustus Maxwell | | Democratic | 1852 | | Incumbent retired.New member elected.Democratic hold. | nowrap | |} Georgia |- ! | James Lindsay Seward | | Democratic | 1853 | Incumbent re-elected. | nowrap | |- !