The motorcycle was westbound on Seashore Highway near Georgetown when it drifted into eastbound lanes and off the road on Saturday morning.
Police say 76-year-old Mary Green of Warrenton, Va., was thrown from the motorcycle as it rode up an embankment and 79-year-old Walter Green was knocked to the ground when the motorcycle hit a wooden post and rail. Walter Green was taken Nanticoke Hospital, where he was pronounced dead. Mary Green was flown to Christiana Hospital in critical condition, but police say she died hours later.
Police are investigating what caused the motorcycle to leave the road.