January 1 – President Abraham Lincoln issues the Emancipation Proclamation.
January 2 — A major battle takes place over three days in Murfreesboro, Tennessee, to become known as the battle of Stone’s River. The forces engaged include the Confederate Army of Tennessee, led by Braxton Bragg, and the Army of the Cumberland led by William Rosecran’s. It is the bloodiest battle to date in terms of casualties weighed against the numbers of men fighting. More than one-third of the Confederates were killed, wounded or captures; and the Union suffered similar casualties. The results boosted Northern morale.
January 20-22 – General Ambrose Burnside gets bogged down in trying to flank the Confederates near Fredericksburg. It becomes a major public relations nightmare known as the Mud March.
January 25 – “Fighting Joe” Hooker replaces Burnside as commander of the Army of the Potomac.
For a complete timeline of the American Civil War see the Civil War Gazette’s timeline here.