Army of the Potomac
The Army of the Potomac was one of the divisions of the Union Army in the Civil War. After March 1864 General Ulysses S. Grant kept his headquarters with the Army of the Potomac during his tenure as commander in chief.
The Confederacy also styled one of its divisions "the Army of the Potomac," though the name was short-lived. After the first Battle of Bull Run, the army was renamed "the Army of Northern Virginia," and Robert E. Lee acceded to the generalship.