- Dec 9 Battle of Bird Creek, Indian Terr (High Shoal, Chusto-Talasah)
- Dec 9 American Civil War: The Joint Committee on the Conduct of the War is established by the U.S. Congress.
- Dec 13 Battle of Alleghany Summit, West Virginia
- Dec 19 Battle of Black Water (American Civil War)
- Dec 20 Battle of Dranesville, VA
- Dec 30 US banks stops payments in gold
- Dec 31 22,990mm of rain falls in Cherrapunji Assam in India in 1861, a world record