A.t. On Old Trolley Line Near The Mason-dixon Line, 01/16/10 Northbound on the A.T. near to the Mason-Dixon Line, the Maryland-Pennsylvania border. For approximately 0.2 miles the A.T. follows an old rail bed for a trolley line which used to transport guests of the former Pen Mar Amusement Park from the park and the railroad station to their quarters in the early 1900s. SoBo 1124.1. NoBo 1055.1.