 The line, MARC's longest at 74 miles, is operated under contract to MARC by Bombardier Transportation and runs on CSX-owned track, including the Metropolitan, Old Main Line, and Cumberland Subdivisions.It is the successor to commuter services provided by the Baltimore & Ohio Railroad (B&O), which date to the mid-19th century.Prior to MARC, the B&O operated commuter trains between Washington and Martinsburg, which continued even after the start of Amtrak on May 1, 1971.