After his victory in the battle of Chancellorsville, Confederate general Robert E. Lee undertook a second invasion of the North. The reorganized Army of Northern Virginia crossed the Potomac (June 17) via the Shenandoah valley, which Richard S. Ewell (2d Corps), as leader of the advance, swept clear of Union forces. By late June, Ewell was seriously threatening Harrisburg, Pa., while Lee, with James Longstreet (1st Corps) and A. P. Hill (3d Corps), was at Chambersburg, Pa. However, with the absence of his cavalry under J. E. B. Stuart, which was raiding in the area between Washington and the position of the Union army, Lee was unable to determine the enemy's strength and movements.
When he finally learned that George G. Meade was concentrating N of the Potomac, he ordered the concentration of his own force. Meade, intending to make his stand at Pipe Creek in Maryland, sent ahead John F. Reynolds, commanding the left wing. But on July 1, John Buford's cavalry, covering Reynolds, came into contact with Harry Heth's division of Hill's corps on the Chambersburg pike just W of Gettysburg. The environs of Gettysburg thus became the unintended site of the greatest battle of the war (July 1–3, 1863).
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.