Adelphi Mill is one of M-NCPPC’s most popular venues for meetings, parties and rentals. Located in the Northwest Branch Stream Valley Park off of Riggs Road, this historic 18th-century mill still retains many of its original millworks. Adelphi Mill is unstaffed and can be reserved through the Park Permit Office by calling 301-699-2400. The Park Permit Office is located at the Department of Parks and Recreation main office building at 6600 Kenilworth Avenue, Ste. 100, Riverdale, MD 20737.