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. Beautiful Mount Airy Mansion is located in this state park, one of the oldest Calvert mansions in Maryland. This is a Maryland State Park. For full information go to the official webpage. (Link on the right side)