History for the day: 1861: The First Battle of Bull Run

History.com has this for 21 July:

In the first major land battle of the Civil War, a large Union force under General Irvin McDowell is routed by a Confederate army under General Pierre G.T. Beauregard.
Three months after the Civil War erupted at Fort Sumter, the Union command still believed the Confederacy could be crushed quickly and with little loss of life. In July, this overconfidence led to a premature offensive into northern Virginia by General McDowell. Searching out the Confederate forces, McDowell led over thirty thousand troops, mostly inexperienced and poorly trained militiamen, toward the railroad junction of Manassas, located just thirty miles from Washington, DC. Alerted to the Union advance, General Beauregard massed some twenty thousand troops there, and was soon joined by General Joseph Johnston, who brought some nine thousand more troops by railroad.
On the morning of 21 July 1861, hearing of the proximity of the two opposing forces, hundreds of civilians– men, women, and children– turned out to watch the first major battle of the Civil War. The fighting commenced with three Union divisions crossing the Bull Run stream, and the Confederate flank driven back to Henry House Hill. However, at this strategic location, Beauregard had fashioned a strong defensive line anchored by a brigade of Virginia infantry under General Thomas J. Jackson. Firing from a concealed slope, Jackson’s men repulsed a series of Federal charges, winning Jackson his famous nickname, Stonewall.
Meanwhile, Confederate cavalry under J.E.B. Stuart captured the Union artillery, and Beauregard ordered a counterattack on the exposed Union right flank. The rebels came charging down the hill, yelling furiously, and McDowell’s line was broken, forcing his troops in a hasty retreat across Bull Run. The retreat soon became an unorganized flight, and supplies littered the road back to Washington. Union forces endured a loss of three thousand men killed, wounded, or missing in action, while the Confederates suffered two thousand casualties. The scale of this bloodshed horrified not only the frightened spectators at Bull Run but also the government in Washington, which was faced with an uncertain military strategy in quelling the “Southern insurrection.”