Events from the year 1866 in the United States.

Incumbents

Federal government

{| class="wikitable collapsible collapsed" ! Governors and lieutenant governors

Governors

• Governor of Alabama: Robert M. Patton (Democratic) • Governor of Arkansas: Isaac Murphy (Democratic) • Governor of California: Frederick Low (Republican) • Governor of Connecticut: William A. Buckingham (Republican) (until May 2), Joseph R. Hawley (Republican) (starting May 2) • Governor of Delaware: Gove Saulsbury (Democratic) • Governor of Florida: David S. Walker (Democratic) • Governor of Georgia: Charles J. Jenkins (Democratic) • Governor of Illinois: Richard J. Oglesby (Republican) • Governor of Indiana: Oliver P. Morton (Republican) • Governor of Iowa: William M. Stone (Republican) • Governor of Kansas: Samuel J. Crawford (Republican) • Governor of Kentucky: Thomas E. Bramlette (Democratic) • Governor of Louisiana: James Madison Wells (Republican) • Governor of Maine: Samuel Cony (Republican) • Governor of Maryland: Augustus Bradford (Unionist) (until January 10), Thomas Swann (Democratic) (starting January 10) • Governor of Massachusetts: John Albion Andrew (Republican) (until January 4), Alexander H. Bullock (Republican) (starting January 4) • Governor of Michigan: Henry H. Crapo (Republican) • Governor of Minnesota: Stephen Miller (Republican) (until January 11), William R. Marshall (Republican) (starting January 11) • Governor of Mississippi: Benjamin G. Humphreys (Democratic) • Governor of Missouri: Thomas Clement Fletcher (Republican) • Governor of Nevada: Henry G. Blasdel (Republican) • Governor of New Hampshire: Frederick Smyth (Republican) • Governor of New Jersey: Joel Parker (Democratic) (until January 16), Marcus Lawrence Ward (Republican) (starting January 16) • Governor of New York: Reuben Fenton (Republican) • Governor of North Carolina: Jonathan Worth (Conservative) • Governor of Ohio: Charles Anderson (Republican) (until January 8), Jacob Dolson Cox (Republican) (starting January 8) • Governor of Oregon: A. C. Gibbs (Republican) (until September 12), George L. Woods (Republican) (starting September 12) • Governor of Pennsylvania: Andrew Gregg Curtin (Republican) • Governor of Rhode Island: James Y. Smith (Republican) (until May 29), Ambrose Everett Burnside (Republican) (starting May 29) • Governor of South Carolina: James Lawrence Orr (Democratic) • Governor of Tennessee: William G. Brownlow (Republican) • Governor of Texas: Andrew J. Hamilton (Democratic) (until August 9), James W. Throckmorton (Democratic) (starting August 9) • Governor of Vermont: Paul Dillingham (Republican) • Governor of Virginia: Francis Harrison Pierpont (Republican) • Governor of West Virginia: Arthur I. Boreman (Republican) • Governor of Wisconsin: James T. Lewis (Republican) (until January 1), Lucius Fairchild (Republican) (starting January 1)

Lieutenant governors

• Lieutenant Governor of Arkansas: Calvin C. Bliss (Republican) • Lieutenant Governor of California: Tim N. Machin (Republican) • Lieutenant Governor of Connecticut: Roger Averill (Republican) (until May 2), Oliver F. Winchester (Republican) (starting May 2) • Lieutenant Governor of Florida: William W. J. Kelly (Republican) • Lieutenant Governor of Illinois: William Bross (Republican) • Lieutenant Governor of Indiana: Conrad Baker (Republican) • Lieutenant Governor of Iowa: Enoch W. Eastman (Republican) (until month and day unknown), Benjamin F. Gue (Republican) (starting month and day unknown) • Lieutenant Governor of Kansas: James McGrew (Republican) • Lieutenant Governor of Kentucky: vacant • Lieutenant Governor of Louisiana: Albert Voorhies (Republican) (until month and day unknown), vacant (starting month and day unknown) • Lieutenant Governor of Maryland: Christopher C. Cox (Unionist) • Lieutenant Governor of Massachusetts: Joel Hayden (Republican) (until January 4), William Clafin (Republican) (starting January 4) • Lieutenant Governor of Michigan: Ebenezer O. Grosvenor (Republican) • Lieutenant Governor of Minnesota: Charles D. Sherwood (Republican) (until January 8), Thomas H. Armstrong (Republican) (starting January 8) • Lieutenant Governor of Missouri: George Smith (Republican) • Lieutenant Governor of Nevada: John S. Crosman (political party unknown) • Lieutenant Governor of New York: Thomas G. Alvord (Republican) (until end of December 31) • Lieutenant Governor of Ohio: vacant (until January 8), Andrew McBurney (Republican) (starting January 8) • Lieutenant Governor of Rhode Island: Duncan Pell (political party unknown) (until May 29), William Greene (political party unknown) (starting May 29) • Lieutenant Governor of South Carolina: W. D. Porter (Democratic) • Lieutenant Governor of Texas: vacant (until August 9), George Washington Jones (Democratic) (starting August 9) • Lieutenant Governor of Vermont: Abraham B. Gardner (Republican) • Lieutenant Governor of Virginia: Leopold Copeland Parker Cowper (Whig) • Lieutenant Governor of Wisconsin: Wyman Spooner (Republican)

Events

January–March

April–June

July–September

October–December

Undated

Ongoing

Births

Deaths