World History Maps Interactive Historical Atlas of the Civil War, detail page for:

Pennsylvania, US Army Department Apr 27, 1861 - Aug 17, 1861

US Dept. of Pennsylvania created Pennsylvania Delaware and parts of Maryland transferred from Dept. of Washington, Apr 27, 1861
Robert Patterson Commander, Apr 27, 1861 - Jul 25, 1861
Western Pennsylvania transferred from US Dept. of Pennsylvania to Dept. of The Ohio, May 9, 1861
Parts of Maryland transferred from US Dept. of Pennsylvania to Dept. of Washington, Jul 25, 1861
US Dept. of Maryland merged into Dept. of Pennsylvania, Jul 25, 1861
Washington and Allegheny counties Maryland transferred from US Dept. of Pennsylvania to Dept. of The Shenandoah, Jul 25, 1861
Western Pennsylvania transferred from US Dept. of The Ohio to Dept. of Pennsylvania, Jul 25, 1861
John A. Dix Commander, Jul 25, 1861 - Aug 17, 1861
US Dept. of The Potomac created Delaware and Maryland transferred from Dept. of Pennsylvania parts of Virginia included Dept. of Pennsylvania discontinued Depts. Of Washington Northeastern Virginia and Shenandoah discontinued absorbed by Dept. of the Poto, Aug 17, 1861