Washington Metro rail service into Washington, D.C. helped breathe life into the region starting in 1978 with the opening of the Silver Spring station. The Metro Red Line was built following the alignment of the B&O Metropolitan Branch, with the Metro tracks centered between the B&O's eastbound and westbound mains. The Red Line heads south to downtown DC from Silver Spring, running at grade before descending into Union Station. By the mid-1990s, the Red Line continued north from the downtown Silver Spring core, entering a tunnel just past the Silver Spring station and running underground to three more stations, Forest Glen, Wheaton and Glenmont.