Rosaryville is a 982 acre day-use park and the location of the historic Mount Airy Mansion. Miles of trails for hiking, biking and equestrians are available for day use. To gain access to Rosaryville State Park, make a right turn into the entrance just south of Osborne Road while traveling south on U.S. 301. Two pavilions, each accommodating 200 guests, are available for rent. A bathroom is a short distance from the pavilion area. A $100 security deposit is required for all pavilion rentals. For pavilion reservations at Rosaryville State Park please call 301-856-9656.