Sterling Price, Confederate governor Claiborne Jackson, Nathaniel Lyon, and Francis Blair meet at Planters' House in St. Louis to discuss a truce. Lyon was quoted as saying "This means war" after the talks end abruptly
(First) Manassas (Confederate)
(First) Bull Run (Union)
About 25 miles southwest of Washington the first major battle of the Civil War pits Irvin McDowell [US] against P. G. T. Beauregard [CS] and Joe Johnston [CS].
Major General John Dix ordered to take command of the Department of Maryland; Brigadier General William S. Rosecrans ordered to take command of the Department of the Ohio
With his troops enlistment expiring, Robert Patterson is relieved of duty in the Shenandoah Valley. He had failed to hold Joseph Johnston in Winchester to prevent Johnston from moving east to support Beauregard at Bull Run.
George McClellan appointed commander, Army of the Potomac, replacing Irvin McDowell. Some sources give the date as July 27, the day he received the orders