The Route 51A circulates through the Town of Upper Marlboro. It serves the Downtown Upper Marlboro, the County Administration Building, and the Marlboro Meadows community located off MD Route 301/Crain Highway. The Route 51A also provides a connection to the Upper Marlboro Branch Library. Route 51A connects with Routes 20, 21, 51B, and 51X at the County Administration Building in Upper Marlboro
Route 51A currently operates with 30 minute frequency. Service span is 6:00 am to 6:00 pm.