Baltimore was on the Pennsylvania Railroad main line between Philadelphia and Washington, now Amtrak. Immediately west of Pennsylvania Station was B&P Jct., where the PRR Northern Central diverged north to York and Harrisburg. Pennsylvania Station was also used by Western Maryland, whose trains actually terminated at Hillen Station, 1 mile southeast of Pennsylvania Station. The Hillen Station spur connected with PRR at Union Jct., immediately east of Pennsylvania Station. The WM line diverged from the PRR line at Fulton Jct., 2 miles west of Baltimore. At Glyndon, 18 miles northwest of Baltimore, WM's Gettysburg Line diverged from the WM Main Line.
Camden Station in both its original and final forms, was a stub station serving Baltimore & Ohio trains operating south to Washington DC. MARC commuter trains presently use that trackage. But between 1896 and 1958, B&O trains operated through, serving Philadelphia and New York to the north. This through operation involved a tunnel underneath Howard Street, trains serving Camden Station using some depressed tracks at the east side of the station immediately south of the tunnel, and an additional stop at Mount Royal Station at the north end of the tunnel. HB Tower controlled the trackage at Camden Station. At Relay, 9 miles west of Baltimore, the Old Main Line which bypassed Washington diverged from the present main line to Washington.
Maryland & Pennsylvania originated at Falls Road Station, operating north into Pennsylvania. Passenger service was discontinued in 1954, and all trackage in Maryland was abandoned in 1958.