! | Donald C. McRuer | | Republican | 1864 | | Incumbent retired.New member elected.Democratic gain. | nowrap | |- ! | William Higby | | Republican | 1863 | Incumbent re-elected. | nowrap | |- ! | John Bidwell | | Republican | 1864 | | Incumbent retired.New member elected.Democratic gain. | nowrap | |} Colorado Territory See non-voting delegates, below. Connecticut Dakota Territory See non-voting delegates, below. Delaware Idaho Territory See non-voting delegates, below. Illinois Indiana Iowa Kansas Kentucky Maine Maryland Massachusetts |- ! | Thomas D. Eliot | | Republican | 1858 | Incumbent re-elected. | nowrap | |- ! | Oakes Ames | | Republican | 1862 | Incumbent re-elected. | nowrap | |- ! | Alexander H. Rice | | Republican | 1858 | |Incumbent retired.New member elected.Republican hold. | nowrap | |- ! | Samuel Hooper | | Republican | 1861 (special) | Incumbent re-elected. | nowrap | |- ! | John B. Alley | | Republican | 1858 | |Incumbent retired.New member elected.Republican hold. | nowrap | |- ! | Nathaniel P. Banks | | Republican | 1865 (special) | Incumbent re-elected. | nowrap | |- ! | George S. Boutwell | | Republican | 1862 | Incumbent re-elected. | nowrap | |- ! | John D. Baldwin | | Republican | 1862 | Incumbent re-elected. | nowrap | |- ! | William B. Washburn | | Republican | 1862 | Incumbent re-elected. | nowrap | |- ! | Henry Laurens Dawes | | Republican | 1856 | Incumbent re-elected. | nowrap | |} Michigan Minnesota Missouri Montana Territory See non-voting delegates, below. Nebraska There were two elections in the new state of Nebraska in 1866: on June 6 for the remainder of the current term, and October 9 for the next term. 39th Congress |- ! | colspan=3 | New state | | New seat.New member elected.Republican gain.New member seated March 2, 1867. | nowrap | |} 40th Congress |- ! | Turner M. Marquett | | Republican | 1866 | | Incumbent retired.New member elected.Republican hold. | nowrap | |} Nevada New Hampshire New Jersey New Mexico Territory See non-voting delegates, below. New York Ohio Democrats gained one seat this election in Ohio. It was later contested and awarded to the Republican for a net gain of zero. |- ! | Benjamin Eggleston | | Republican | 1864 | Incumbent