The Route 51B circulates through the Town of Upper Marlboro.  It serves the Dutch Village Farmer’s Market at Old Marlboro Pike and John Rogers Boulevard, downtown Upper Marlboro, the County Administration Building, and the Marlboro Village Community. The Route 51B also provides a connection to the Upper Marlboro Branch Library.  Route 51B connects with Routes 20, 21, 51A, and 51X at the County Administration Building in Upper Marlboro

Route 51B currently operates with 30 minute frequency.  Service span is 6:00 am to 6:00 pm.