1861 1862 1863 - 1864 - 1865 1866 1867
| Decades: |
1830s 1840s 1850s - 1860s - 1870s 1880s 1890s
| Centuries: |
18th century - 19th century - 20th century
January - March
- January 21 - Maori Wars: The Tauranga Campaign starts.
- February 27 - American Civil War: The first Northern prisoners arrive at the Confederate prison at Andersonville, Georgia.
- March 1- [[Alejandro Mon Men�ndez]] takes office as Prime Minister of Spain
- March 10 - American Civil War: The Red River Campaign begins as Union troops reach Alexandria, Louisiana.
- March 11 - A reservoir near Sheffield bursts; 250 dead
April - June
- 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 18 – Civil War gold hoax - New York World and the New York Journal of Commerce publish a fake proclamation that president Abraham Lincoln has issued a draft of 400.000 more soldiers
- 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.
- June 5 - American Civil War: Battle of Piedmont - Union forces under General David Hunter defeat a Confederate army at Piedmont, West Virginia, taking nearly 1,000 prisoners.
- June 10 - American Civil War: Battle of Brice's Crossroads - Confederate troops under Nathan Bedford Forrest defeat a much larger Union force led by General Samuel D. Sturgis in Mississippi.
- June 12 - American Civil War: Battle of Cold Harbor: - General Ulysses S. Grant pulls his troops from their positions at Cold Harbor, Virginia and moves south.
- June 15 - Arlington National Cemetery is established when 200 acres (0.8 km²) of Arlington Mansion are officially set-aside as a military cemetery by U.S. Secretary of War Edwin M. Stanton.
- June 15 - American Civil War: Battle of Petersburg begins - Union forces under General Grant and troops led by Confederate General Robert E. Lee battle for the last time.
July - September
- July 18 - President Lincoln issues a true proclamation of conscription of 500.000 men for the US Civil War
- 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.
- June 21 - Maori Wars: The Tauranga Campaign ends.
- July 22 - American Civil War: Battle of Atlanta - Outside of Atlanta, Georgia, Confederate General Hood leads an unsuccessful attack on Union troops under General 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 Hood make a third unsuccessful attempt to drive Union forces under General 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 1 - foundation of Elgin Watch Company in Elgin, Illinois
- 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 - December
- October 2 - American Civil War: Battle of Saltville - Union forces attack Saltville, Virginia but are defeated by Confederate troops.
- October 5 – Cyclone kills 70.000 in Calcutta, India
- 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 Sherman burns Atlanta 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 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
- Danevirke 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. He also condemns rationalism and socialism
- Principality of Abkhazia annexed by Russia
- Haiti declares independence
- Brazil invades Uruguay in support of Venancio Flores. Paraguay attacks Brazil.
- 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 (d. 1928)
- January 24 - Marguerite Durand, journalist and feminist leader (d. 1936)
- March 13 - Alexej von Jawlensky, Russian impressionist painter
- March 15 - Johan Halvorsen, Norwegian composer
- March 19 - Charles Marion Russell, artist (+ 1926)
- April 21 - Max Weber, sociologist (+ 1920)
- May 10 - [[L�on Gaumont]], French film pioneer (d. 1946)
- July 13 - John Jacob Astor IV, American businessman, inventor (+ 1912)
- October 25 - Alexander Tikhonovich Grechaninov, composer (+ 1956)
- November 24 - Henri de Toulouse-Lautrec, painter
- December 6 - William S. Hart, silent film star (+ 1946)
- January 13 - Stephen Foster, composer of Camptown Races, Oh! Susannah
- May 19 - Nathaniel Hawthorne, author
- December 19 - Pierre-Joseph Proudhon, anarchist
- 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 with nitroglycerin.af:1864
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