Between September 4th and 7th, 1862, the Army of Northern Virginia, General Robert E. Lee, commanding, crossed the Potomac near Leesburg and occupied Frederick, Maryland. On the 10th a movement was made to surround and capture the Union forces at Harper's Ferry. Early that morning Major-General T. J. Jackson, with Jackson's (Stonewall) Division and the divisions of R.S. Ewell and A.P Hill, left Frederick, marched over South Mountain at this Pass, crossed the Potomac near Williamsport on the 11th, seized Martinsburg on the 12th and marching by way of Charlestown, invested Harper's Ferry from the Virginia side of the Potomac on the 13th. J.G. Walker's Division, then near Monocacy Aqueduct, recrossed the Potomac at Point of Rocks on the night of the 10th, and occupied Loudon Heights on the 13th. Major-General Lafayette McLaws with his own division and R.H. Anderson's both of Longstreet's command, moved from Frederick on the 10th, via Middletown; crossed South Mountain at Brownsville Pass, seven miles south of this, on the 11th; Two brigades moved unto Maryland Heights and six down Pleasant Valley on the 12th, and invested Harper's Ferry from the Maryland side. Generals Lee and Longstreet, with the divisions of D.R. Jones and J.B. Hood, the brigade of N.G. Evans and the Reserve Artillery, marched on this road to Hagerstown. D.H. Hill's Division halted at Boonsboro to prevent the escape of the garrison at Harper's Ferry through Pleasant Valley and to support Stuart's Cavalry, which remained east of South Mountain to observe the movements of the Union Army and retard its advance.