After two brief engagements in Loudoun County at Heaton's Crossroads (present day Purcellville) and Woodgrove on July 16, Early's main force crossed west over the Blue Ridge Mountains at Snickers Gap and established themselves around Berryville. To cover his rear, Early left substantial rearguard forces at main river crossings of the Shenandoah River. On July 17, the Union cavalry passed westward through Snicker's Gap and unsuccessfully attempted to force passage of the river at Castleman's Ferry (Snicker's Ford).