After marching north through the Shenandoah Valley from Lynchburg, the Confederate army of Lieutenant General Jubal A. Early side-stepped the Federal garrison at Harpers Ferry and crossed the Potomac River at Shepherdstown into Maryland on July 5-6.
On July 9, 1864, a makeshift Union force under Major General Lew Wallace attempted to arrest Early's invading Confederate divisions along the Monocacy River, just east of Frederick.
Wallace, joined by Ricketts's Division of the VI Corps that had been rushed from the Petersburg lines, was outflanked by Gordon's Division and defeated after putting up a stiff resistance.
Hearing of Early's incursion into Maryland, Grant embarked the rest of the VI Corps on transports at City Point, sending it with all dispatch to Washington.
Wallace's defeat at Monocacy bought time for these veteran troops to arrive to bolster the defenses of Washington.
Early's advance reached the outskirts of Washington on the afternoon of July 11, and the remaining divisions of the VI Corps began disembarking that evening.
Monocacy was called the "Battle that Saved Washington."
Result(s): Confederate victory
Location: Frederick County
Campaign: Early's Raid and Operations against the B&O Railroad (June-August 1864) next battle in campaign Campaigns
Date(s): July 9, 1864
Principal Commanders: Major General Lew Wallace [US]; Lieutenant General Jubal A. Early [CS]
Forces Engaged: Corps
Estimated Casualties: 2,359 total