Great Cacapon is a census-designated place in Morgan County in the U.S. state of West Virginia's Eastern Panhandle. As of the 2010 census, its population was 386.Great Cacapon takes its name from the Cacapon River which empties into the Potomac River to the town's east. It was originally known as Cacapon Depot on the Baltimore and Ohio Railroad mainline when a post office was established here in 1848.