The Route 51X circulates from the Equestrian Center parking areas to the County Administration Building and County Courthouse. The Route 51X operates along Water Street and Governor Oden Bowie Drive serving downtown Upper Marlboro and commuter parking lots at the Equestrian Center Route 51X connects with Routes 20, 21, 51A and 51B at the County Administration Building in Upper Marlboro.

Route 51X currently operates staggered headways throughout the day ranging from 5 minutes in peak periods to 15 minutes in the off peak period. Service span is 6:00 am to 7:00 pm.