Decades: 1810s1820s1830s1840s1850s - 1860s - 1870s1880s1890s1900s1910s
- February 27 - American Civil War: The first Northern prisoners arrive at the Confederate prison at Andersonville, Georgia.
- April 22 - The United States Congress passes the Coinage Act of 1864 which mandates that the inscription "In God We Trust" needs to be placed on all coins minted as United States currency.
- James Clerk Maxwell discovers Microwaves
- First Geneva Convention
- August 22 - International Red Cross founded in Geneva, Switzerland
- November - Abraham Lincoln defeats George B. McClellan in the U.S. presidential election
- Vatican, Syllabus errorum. Pope Pius IX condemns theological liberalism as an error and claims for the supremacy of RC Church authority over the civil society.
- 1864 in literature:
- January 13 -- Wilhelm Wien, physicist
- March 13 - Alexej von Jawlensky, Russian impressionist painter
- March 19 - Charles Russell, artist
- April 21 - Max Weber, sociologist
- November 24 - Henri de Toulouse-Lautrec, painter
- January 13 - Stephen Foster, composer of Camptown Races, Oh! Susannah
- Roger Taney - United States Supreme Court Justice
- Tuanku Imam Bonjol - Indonesian religious and military leader