Howard Street Tunnel interior
Two people stand inside the Howard Street Tunnel in Baltimore, Maryland. Constructed by the Baltimore Belt Line, which was a wholly-owned subsidiary of the Baltimore & Ohio Railroad, the tunnel was built between 1890 to 1895 and was the longest in the B&O system at 1.4 miles. The Baltimore Belt Line was created in order to connect the B&O Railroad's newly constructed line to Philadelphia and New York City with the rest of the railroad at Baltimore. It included the Howard Street Tunnel, the Mount Royal Station, and the first mainline railroad electrification in the United States.