The Army of The Potomac, was the Main Army Contingent of The Union Army during the American Civil War (1861-1865). As previously see, Armies were identified by various flags and standards. Conversely, Commanding Generals had their own personal "Colors". Called a "Flag", The designation for The Army of The Potomac had changed several times since the start of the War. In 1863, when Gen. George Meade took command (just prior to The Battle of Gettysburg), it is said he designed these Colors. Although traditionally "Guidon shaped" it's size classified it as a Flag. It was flown outside of where ever the Command Tent of The Army was set up, or carried along side the General, when he was on horse or in wagon.
Measuring at 4 feet by 4 feet, it was an early nature Maroon Field. In the far left portion if the Flag, was a Golden colored Union Eagle. This flag was replaced when Gen. Grant took command in late 1863.