1864

• February 27 - American Civil War: The first Northern prisoners arrive at the Confederate prison at Andersonville, Georgia.
• March 10 - American Civil War: The Red River Campaign begins as Union troops reach Alexandria, Louisiana.
• April 22 - The United States Congress passes the Coinage Act of 1864 which mandates that the inscription "In God We Trust" be placed on all coins minted as United States currency.
• May 7 - American Civil War: The Army of the Potomac, under General Ulysses S. Grant, breaks off from the Battle of the Wilderness and moves southwards.
• May 11 - American Civil War: Battle of Yellow Tavern - Confederate General JEB Stuart is mortally wounded at Yellow Tavern, Virginia.
• May 12 - American Civil War: Battle of Spotsylvania Court House: The "Bloody Angle" - thousands of Union and Confederate soldiers die.
• May 13 - American Civil War: Battle of Resaca - the battle begins with Union General Sherman fighting toward Atlanta.
• May 15 - American Civil War: Battle of New Market, Virginia - Students from the Virginia Military Institute fight alongside the Confederate Army to force Union General Franz Sigel out of the Shenandoah Valley.
• May 20 - American Civil War: Battle of Bermuda Hundred - In Virginia, 3,000 Confederates and l,200 Union troops are killed in this Union victory.
• May 26 - Montana is organized as a United States territory.
• July 20 - American Civil War: Battle of Peachtree Creek - Near Atlanta, Georgia, Confederate forces led by General John Bell Hood unsuccessfully attack Union troops under General William T. Sherman.
• July 22 - American Civil War: Battle of Atlanta - Outside of Atlanta, Georgia, Confederate General John Bell Hood leads an unsuccessful attack on Union troops under General William T. Sherman on Bald Hill.
• July 24 - American Civil War: Battle of Kernstown - Confederate General Jubal Early defeats Union troops led by General George Crook in an effort to keep the Yankees out of the Shenandoah Valley.
• July 28 - American Civil War: Battle of Ezra Church begins - Confederate troops led by General John Bell Hood make a third unsuccessful attempt to drive Union forces under General William T. Sherman from Atlanta, Georgia.
• July 29 - American Civil War: Confederate spy Belle Boyd is arrested by Union troops and detained at the Old Capitol Prison in Washington, DC.
• July 30 - American Civil War: Battle of the Crater - Union forces attempt to break Confederate lines by exploding a large bomb under their trenches.
• August 5 - American Civil War: Battle of Mobile Bay begins - At Mobile Bay near Mobile, Alabama, Admiral David Farragut leads a Union flotilla through Confederate defenses and seals one of the last major Southern ports.
• August 18 - American Civil War: Battle of Weldon Railroad - Forces under Union General Ulysses S. Grant try to cut a vital Confederate supply-line into Petersburg, Virginia, by attacking the Weldon Railroad forcing the Confederates to use wagons.
• August 22 - International Red Cross founded in Geneva, Switzerland.
• September 1 - American Civil War: Confederate General John Bell Hood evacuates Atlanta, Georgia after a four month siege mounted by Union General William T. Sherman.
• September 1 - 8 - Delegates from the Canadian colonies meet at the Charlottetown Conference to discuss Canadian Confederation.
• September 2 - American Civil War: Union forces under General William T. Sherman enter Atlanta, Georgia a day after the Confederate defenders fled the city.
• September 7 - American Civil War: Atlanta, Georgia is evacuated on orders of Union General William Tecumseh Sherman.
• October 2 - American Civil War: Battle of Saltville - Union forces attack Saltville, Virginia but are defeated by Confederate troops.
• October 9 - American Civil War: Battle of Tom's Brook - Union cavalrymen in the Shenandoah Valley defeat Confederate forces at Tom's Brook, Virginia.
• October 28 - American Civil War: Second Battle of Fair Oaks ends - Union forces under General Ulysses S. Grant withdraw from Fair Oaks, Virginia, after failing to breach the Confederate defenses around Richmond, Virginia.
• October 30 - Second war of Schleswig concluded. Duke Frederick and the Danish Crown recognize Prussia's and Austria's annexation of Schleswig, Holstein and Lauenburg.
• October 30 - Helena, Montana is founded after four prospectors discover gold at "Last Chance Gulch."
• October 31 - Nevada is admitted as the 36th U.S. state.
• November 4 - American Civil War: Battle of Johnsonville - At Johnsonville, Tennessee, troops under the command of Confederate General Nathan Bedford Forrest bombard a Union supply base with artillery and destroy millions of dollars in materiel.
• November 8 - U.S. presidential election, 1864: Abraham Lincoln is reelected in an overwhelming victory over George McClellan.
• November 15 - American Civil War: Sherman's March to the Sea begins - Union General William Tecumseh Sherman burns Atlanta, Georgia and starts to move south, destroying everything in his path in order to punish the Confederates for starting the war.
• November 22 - American Civil War: Sherman's March to the Sea: Confederate General John Bell Hood invades Tennessee in an unsuccessful attempt to draw Union General Sherman from Georgia.
• November 29 - Indian Wars: Sand Creek Massacre - Colorado volunteers led by Colonel John Chivington massacre at least 400 Cheyenne and Arapahoe noncombatants at Sand Creek, Colorado (where they had been given permission to camp).
• November 30 - American Civil War: Battle of Franklin - The Army of Tennessee led by General John Bell Hood mounts a dramatically unsuccessful frontal assault on Union positions around Franklin, Tennessee (Hood lost six generals and almost a third of his troops).
• December 4 - American Civil War: Sherman's March to the Sea - At Waynesboro, Georgia, forces under Union General Judson Kilpatrick prevent troops led by Confederate General Joseph Wheeler from interfering with Union General Sherman's campaign of destroying a wide swath of the South on his march to the Gulf of Mexico (Union forces did suffer more than three times the casualties as the Confederates, however).

• James Clerk Maxwell discovers Microwaves
• First Geneva Convention
• Dannevirke destroyed
• Syllabus errorum: Pope Pius IX condemns theological liberalism as an error and claims for the supremacy of RC Church authority over the civil society.
• Principality of Abkhazia annexed by Russia

• 1864 in literature
• 1864 in science
• 1864 in music

• January 8 - Prince Albert Victor, Duke of Clarence, second in line to the throne of the United Kingdom of Great Britain and Ireland.
• January 13 -- Wilhelm Wien, physicist
• March 13 - Alexej von Jawlensky, Russian impressionist painter
• March 19 - Charles Marion Russell, artist (+ 1926)
• April 21 - Max Weber, sociologist (+ 1920)
• July 13 - John Jacob Astor IV, American businessman, inventor (+ 1912)
• October 25 - Alexander Tikhonovich Grechaninov, composer (+ 1956)
• November 24 - Henri de Toulouse-Lautrec, painter

• January 13 - Stephen Foster, composer of Camptown Races, Oh! Susannah
• May 19 - Nathaniel Hawthorne, author
• Roger Taney - United States Supreme Court Justice
• Tuanku Imam Bonjol - Indonesian religious and military leader
• Emil Nobel - the younger brother of Alfred Nobel killed in their experiments of nitroglycerin.