Events of 1864
January - March
February 17: submarine Hunley
* January 16 - Denmark rejects a Prussian-Austrian ultimatum to repeal the Danish Constitution.[1][2]
* January 21 - Māori Wars: The Tauranga Campaign starts.
* February 1 - Danish-Prussian War (Second war of Schleswig): 57,000 Austrian and Prussian troops cross the Eider River into Denmark.
* February 17 - American Civil War: The tiny Confederate submarine Hunley torpedoes the USS Housatonic, becoming the first submarine to sink an enemy ship (the sub and her crew of 8 are also lost).
* February 25 - American Civil War: The first Northern prisoners arrive at the Confederate prison at Andersonville, Georgia (the 500 prisoners had left Richmond, Virginia 7 days before).
* March 1- Alejandro Mon Menéndez takes office as Prime Minister of Spain.
* March 9- American Civil War: Abraham Lincoln appoints Ulysses S. Grant commander in chief of all Union armies.
* March 10 - American Civil War: The Red River Campaign begins as Union troops reach Alexandria, Louisiana.
* March 11 - A reservoir near Sheffield, England bursts; 250 die.
April - June
American Civil War in 1864
* April 18 - Danish-Prussian War (Second War of Schleswig) - Battle of Dybbøl: The Prussian army fielding 10,000 men defeats the Danish defending army of 9,200 at Dybbøl Mill, after an artillery bombardment from April 7 to April 18.
* April 22 - The U.S. 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 5 - American Civil War: The Battle of the Wilderness begins in Spotsylvania County, Virginia.
* 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 18 - Civil War gold hoax: The 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 Ware Bottom Church: In the Virginia Bermuda Hundred Campaign, 10,000 troops fight in this Confederate victory.
* May 21 - Circassian leaders sign Russian loyalty oaths, ending the Russian-Circassian War.
* May 28 - Montana is organized as a United States territory out of parts of Washington Territory and Dakota Territory, and is signed into law by President Abraham Lincoln.
May 13: Battle of Resaca.
* 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 the grounds of Robert E. Lee's home Arlington House are officially set-aside as a military cemetery by U.S. Secretary of War Edwin M. Stanton.
* American Civil War - Battle of Petersburg: Union forces under General Grant and troops led by Confederate General Robert E. Lee battle for the last time.
* June 21 - Māori Wars: The Tauranga Campaign ends.
* June 27 - American Civil War: Battle of Kennesaw Mountain near Kennesaw, Georgia.
August 5: Battle of Mobile Bay.
July - September
* July 18 - President Lincoln issues a true proclamation of conscription of 500,000 men for the U.S. 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.
* 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: 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 - The Elgin Watch Company is founded in Elgin, Illinois.
* August 5 - American Civil War - Battle of Mobile Bay: 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 13 - The first fish and chips shop opens in London.
* August 18 - American Civil War - Battle of Globe Tavern: 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 - First Geneva Convention: The International Red Cross is founded.
* August 31 - American Civil War: Union forces led by General William T. Sherman launch an assault on Atlanta, Georgia.
Aug. 22: Red Cross
* September 1 -American Civil War: Confederate General Hood evacuates Atlanta after a 4-month siege mounted by Union General Sherman.
* September 2 - American Civil War: Union forces under General Sherman enter Atlanta 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.
* September 8 - Delegates from the Canadian colonies meet at the Charlottetown Conference to discuss the Canadian Confederation.
[edit] October - December
* October 2 - American Civil War - Battle of Saltville: Union forces attack Saltville, Virginia but are defeated by Confederate troops.
* October 5 - A 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: Union forces under General Ulysses S. Grant withdraw from Fair Oaks, Virginia, after failing to breach the Confederate defenses around Richmond, Virginia.
* October 30
o The Second war of Schleswig is concluded. Denmark renounces all claim to Schleswig, Holstein and Lauenburg, which come under Prussian and Austrian administration.
o Helena, Montana is founded after four prospectors (the so-called Four Georgians) discover gold at Last Chance Gulch; it is their last and agreed final attempt at weeks of trying to find gold in the northern Rockies.
* 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 material.
* November 7 - The capital of Idaho Territory is moved from Lewiston to Boise; North Idaho declares the move illegal and proposes secession.
* November 8 - U.S. presidential election, 1864: Abraham Lincoln is reelected in an overwhelming victory over George B. McClellan.
* November 15 - American Civil War - Sherman's March to the Sea begins: Union General Sherman burns Atlanta and starts to move south, causing extensive devastation to crops and mills and living off the land.
* November 20 - The Judicial reform of Alexander II is launched in Imperial Russia.
* 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 25 - American Civil War: A group of Confederate operatives calling themselves the Confederate Army of Manhattan starts fires in more than 20 locations in an unsuccessful attempt to burn down New York City.
* 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).
Nov.15: Sherman's March to the Sea.
* November 30 - American Civil War - Second Battle of Franklin: The Army of Tennessee led by General Hood mounts a dramatically unsuccessful frontal assault on Union positions around Franklin, Tennessee (Hood loses 6 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 Savannah, GA (Union forces suffer more than 3 times the casualties as the Confederates, however).
* December 8 - Syllabus errorum: Pope Pius IX condemns theological liberalism as an error and claims for the supremacy of Roman Catholic Church authority over the civil society. He also condemns rationalism and socialism.
* December 15-16 - American Civil War - Battle of Nashville: Union forces decisively defeat the Confederate Army of Tennessee.