Baltimore and Potomac Tunnel
The Baltimore and Potomac Tunnel (or B&P Tunnel) is a double track, masonry arch railroad tunnel on the Northeast Corridor in Baltimore, Maryland, immediately to the south of Pennsylvania Station. Approximately 140 Amtrak and MARC passenger trains, as well as two freight trains, use the tunnel daily.
The 7,669-foot (2,338 m) tunnel facility, which passes under the Baltimore neighborhoods of Bolton Hill, Madison Park, and Upton, consists of a series of three tunnel sections—Gilmor Street Tunnel, Wilson Street Tunnel, and John Street Tunnel—delineated by two open air cuts—Pennsylvania Avenue Opening and John Street Opening.
Constructed by the Baltimore and Potomac Railroad under Winchester Street and Wilson Street in Baltimore, the tunnel opened on June 29, 1873. The B&P tunnel allowed the Pennsylvania Railroad (PRR) direct access to Washington, D.C. for the first time by connecting its Northern Central Railway affiliate (which arrived in Baltimore from the north) to the Baltimore and Potomac's new spur, which ran to Washington.
Between 1916 and 1917, the PRR lowered the floor of the tunnel approximately 2 1⁄2 feet to accommodate larger trains. The work included the underpinning of the side walls, installation of a concrete invert slab, and reconstruction of the track structure. The bases of the tunnel walls were chipped away to improve horizontal clearance.
Prior to the electrification of the PRR's New York City to Washington main line in 1935, the poorly-ventilated tunnel easily filled with smoke from the steam locomotives then in use. The smoke also was a nuisance to the residential neighborhoods above the tunnel.
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