The first major battle of the Civil War took place July 21, 1861, near Manasses, Va. The First Battle of Bull Run, also called the First Battle of Manasses, involved 15,000 Union and 14,000 Confederate soldiers.
The Confederate victory sent Union troops retreating toward Washington, DC. Michael O. Varhola, the author of Life in Civil War America, reports that 460 men were killed and 1,124 wounded on the Union side, and 387 killed and 1,582 wounded on the Confederate side.
This was the battle where Confederate Gen. Thomas Jonathan Jackson, relatively unknown until then, got the nickname Stonewall for standing his ground.
Soon after the battle, President Lincoln replaced Gen. Irvin McDowell with Maj. Gen. George B. McClellan. The North was shocked by the loss, and both sides began to realize they were in for a longer, bloodier war than expected.