The Flat Rock Tunnel is an active railroad tunnel near Manayunk, Pennsylvania

Pennsylvania

The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

, USA. The tunnel was built by the Reading Railroad

Reading Company

The Reading Company , usually called the Reading Railroad, officially the Philadelphia and Reading Rail Road and then the Philadelphia and Reading Railway until 1924, operated in southeast Pennsylvania and neighboring states...

 for its line along the Schuylkill River

Schuylkill River

The Schuylkill River is a river in Pennsylvania. It is a designated Pennsylvania Scenic River.The river is about long. Its watershed of about lies entirely within the state of Pennsylvania. The source of its eastern branch is in the Appalachian Mountains at Tuscarora Springs, near Tamaqua in...

.

Construction of the tunnel started in 1836 and it opened in 1840. In 1858-9 the Flat Rock and Black Rock Tunnel

Black Rock Tunnel

The Black Rock Tunnel is an active rail road tunnel of the old Reading Railroad. The 1835 tunnel was the second rail tunnel constructed in the United States, and is the oldest still in use. The tunnel is also notable as being the first for which shafts were sunk during construction. The tunnel...

s were widened to accommodate the wider rolling stock from the Lebanon Valley Branch

Lebanon Valley Railroad

The Lebanon Valley Railroad is a railroad line between Harrisburg and Reading in Pennsylvania, USA. The line opened on 18 January 1858.The road was acquired by the Reading Railroad on 20 March 1858, which put them in direct competition with the Pennsylvania Railroad for the Philadelphia to...

. The spacing between the tracks was increased from 4 feet (1.2 m) to 6 feet (1.8 m). The widening of the tunnel was the first project to employ electric detonation of multiple explosive charges.

External links

• Historic American Engineering Record (HAER) No. PA-539, "Philadelphia & Reading Railroad, Flat Rock Tunnel"