Baltimore and Potomac Tunnel

The Baltimore and Potomac Tunnel (or B&P Tunnel) is a double-tracked, masonry arch railroad tunnel on the Northeast Corridor in Baltimore, Maryland, just west of Pennsylvania Station (Baltimore). Opened in 1873, the tunnel is the oldest tunnel operated by Amtrak. In 2008, the tunnel was used by about 140 Amtrak and MARC passenger trains and two freight trains every day.

The 7,669-foot (2,338 m) tunnel, which passes under the Baltimore neighborhoods of Bolton Hill, Madison Park, and Upton, is a single tube with two tracks. It is punctuated by two open-air cuts for ventilation of exhaust fumes and smokePennsylvania Avenue Opening and John Street Openingthat divide the main tunnel into three "sub-tunnels", designated (from south to north) Gilmor Street Tunnel, Wilson Street Tunnel, and John Street Tunnel.