Great Appalachian Valley

West of Frederick, beyond South Mountain, is the Cumberland Valley.

This is the northern half of the Great Valley that sweeps northeastward through Virginia, Maryland, and Pennsylvania.

That part of the Great Valley immediately south of the Potomac is called the Shenandoah Valley.

Lee planned to concentrate his army west of the mountains near Hagerstown, Maryland.

There, he would be in direct line with his supply base at Winchester in the Shenandoah Valley.

West of Frederick, beyond South Mountain, is the Cumberland Valley.

This is the northern half of the Great Valley that sweeps northeastward through Virginia, Maryland, and Pennsylvania.

That part of the Great Valley, immediately south of the Potomac, is called the Shenandoah Valley.

lee planned to concentrate his army west of the mountains near hagerstown maryland there he would be in direct line with his supply base at winchester in the shenandoah valley after replenishing his supplies and ammunition he could strike northeast through the cumberland valley toward harrisburg pa where he could destroy the Pennsylvania Railroad Bridge across the Susquehanna River.

Once loose in the middle of Pennsylvania, he could live off the country and threaten Philadelphia, Baltimore, and Washington.