The B&P Tunnel system was completed in 1873, running under several West Baltimore neighborhoods including Bolton Hill, Madison Park, and Upton. The tunnel connects Baltimore's Pennsylvania Station to points south including Washington, DC. It is one of the oldest structures on the Northeast Corridor. The tunnel is approximately 7,500 feet (1.4 miles) long and is comprised of three shorter tunnels: the John Street Tunnel, the Wilson Street Tunnel, and the Gilmor Street Tunnel. The narrow-profile, single-bored, double-track tunnel was originally constructed out of brick and stone masonry, though repairs have added additional building materials over time. Electrification was added in the 1930s, and the tunnel was rehabilitated in the 1980s. However, that work was not intended as a permanent fix and continual repairs are required to maintain the aging structures.