The Baltimore and Potomac Railroad opened the 7,669-foot-long Baltimore and Potomac Tunnel in 1873.
The tunnel opened on June 29, 1873, and is a single tube with two tracks. The tunnel’s construction required 13 million bricks, and the waste dirt was used to shore up several areas of the city, allowing for more homes and buildings to be constructed.
Between 1916 and 1917, the Pennsylvania Railroad expanded the tunnel to accommodate larger trains.
