| John Quincy Adams | | Whig | 1830 | | Incumbent died February 23, 1848.New member elected April 3, 1848.Whig hold.Successor later re-elected for the next term, see below. | nowrap | |- ! | James A. Black | | Democratic | 1843 | | Incumbent died April 3, 1848.New member elected October 10, 1848.Democratic hold.Successor later re-elected for the next term, see below. | nowrap | |- ! | John M. Holley | | Whig | 1846 | | Incumbent died March 8, 1848.New member elected November 7, 1848.Whig hold.Successor later re-elected for the next term, see below. | nowrap | |- ! | Alexander D. Sims | | Democratic | 1844 | | Incumbent died November 22, 1848.New member elected January 9, 1849.Democratic hold.Successor later elected for the next term, see below. | nowrap | |- ! | | | | New delegate elected October 30, 1848. |} 31st Congress |- ! | Alexander D. Sims | | Democratic | 1844 | | Incumbent had been re-elected, see below, but died November 22, 1848.New member elected January 16, 1849.Democratic.Successor having already been elected to finish the current term, see above. | nowrap | |- ! | Rodolphus Dickinson | | Democratic | | Incumbent died March 20, 1849.New member elected in 1849. |- ! | | | |- ! | | | |} Alabama Elections were held August 6, 1849, after the March 4, 1849 beginning of the term, but before the House first convened in December 1849. |- ! |- ! |- ! |- ! |- ! |- ! |- ! |} Arkansas The election was held August 7, 1848. |- ! |} California California two at-large members were elected November 11, 1849 in anticipation of statehood and seated September 11, 1850. |- ! rowspan=2 | | colspan=3 | None | | New seat.New member elected.Independent gain. | rowspan=2 nowrap | |- | colspan=3 | None | | New seat.New member elected.Democratic gain. |} Connecticut Elections were held April 2, 1849, after the March 4, 1849 beginning of the term, but before the House first convened in December 1849. |- ! |- ! |- ! |- ! |} Delaware The election was held November 6, 1848. |- ! |} Florida Florida's single at-large member was elected October 2, 1848. |- ! | Edward C. Cabell | | Whig | 1846 | Incumbent re-elected. | nowrap |