January 11

Edwin Stanton replaces Simon Cameron as Union secretary of war

February 16

Ulysses S. Grant takes Fort Donelson in Tennessee

February 21

The Battle at Valverde, in the New Mexico Territory, results in a Confederate victory

February 25

Nashville, Tennessee, falls to the Union without a fight

March 7–8

Confederate general Earl Van Dorn attempts to defeat Union forces at the Battle of Pea Ridge but is pushed back

March 9

The Union ironclad Monitorand Confederate ironclad Virginiaengage in a duel at Hampton Roads, Virginia; the battle ends in a draw

March 11

Lincoln demotes McClellan from general-in-chief to commander of the Army of the Potomac

April 4

The Peninsular Campaign begins with a Union advance toward Yorktown, Virginia; Yorktown falls to the Union on May 4, and Williamsburg falls on May 5

April 6–7

The Battle of Shiloh results in a Confederate withdrawal from Pittsburg Landing, Tennessee.

April 7

Island No. 10 falls to Union land and naval forces, placing the Mississippi River under Union control all the way to Memphis

April 10

Lincoln signs a congressional resolution calling for gradual emancipation and the compensation of slave owners; slavery is also abolished in Washington, D.C.

April 25–May 1

The Battle of New Orleans

May 12

Natchez, Mississippi, also falls to the Union

June 1

Joseph Johnston is wounded in battle and is replaced by Robert E. Lee as leader of the Confederacy's Virginia forces

June 6

Union forces take Memphis, Tennessee

June 25–July 2

The Seven Days Battles results in a Union retreat and temporarily ends the Union threat to Richmond

June 30

The Union attempts to capture Tampa via gunboats, but Confederates refuse to surrender or retreat

July 20

Congress authorizes the acceptance of African Americans into military service and passes a second Confiscation Act that frees slaves belonging to all rebels

July 11

Lincoln names Henry Halleck as general-in-chief

August 28–30

The Second Battle of Manassas ends with a Union defeat; General John Pope, who led the Union forces, is replaced by McClellan

September 17

The Battle of Antietam in Maryland becomes the single bloodiest day of the war; though technically a draw, the battle forces Lee to abort his planned invasion of the North

September 27

The First Regiment Louisiana Native Guards becomes the first officially recognized black regiment

October 4

Union forces attack and occupy Galveston Harbor in Texas

October 8

The Battle of Perryville, Kentucky, stops a second Confederate invasion of the North

November 5

Lincoln dismisses McClellan a second time and replaces him with Ambrose Burnside

December 13

The Battle of Fredericksburg, Virginia, results in a Union rout with numerous casualties

December 31

The Battle of Murfreesboro, Tennessee begins; it ends inconclusively with a Confederate retreat on January 2, 1863