Camp Hill was the site of the defining battle of the War of Secession. In September 1862, Confederate General Robert E. Lee's Army of Northern Virginia invaded the North and was able to steal a march on Union General George McClellan's Army of the Potomac. This was due in part to McClellan's own sluggishness on the march and in part to the Union Army's Intelligence officers' failure to locate the major columns of the Army of Northern Virginia. (In fact, the Army was divided through much of the march. Had McClellan known this, and had he acted aggressively, he may well have been able to destroy Lee's army.)