Point Lookout Lighthouse
Located at the confluence of the Potomac River and the Chesapeake Bay, it was one of the oldest lighthouses on the Chesapeake and is still in use, but automated.  The structure has been under the control of the U. S. Navy for decades, which has used it as a tracking station and it bristles with electronic equipment.  It has opened once a year for ghost walks as some locals swear it is haunted.  The site was a Union Army Prisoner of War Camp where as many as 14,000 Confederate prisoners died due to abuse and poor conditions.  A monument to the dead is nearby. 
The site now is adjacent to the State of Maryland Point Lookout State Park with excellent shore fishing, pier fishing and fishing from a series of seawalls.  Camping is available and fills up early.