Pennsylvania Canal Tunnel

Construction was authorized February 8, 1827,^[6] and the tunnel was completed November 10, 1829.^[1] The canal crossed the Allegheny River on a covered bridge aqueduct, later replaced by John A. Roebling's first suspension bridge, the Allegheny Aqueduct.,^[7] the canal traveled underground through most of downtown Pittsburgh, under Grant's Hill, to end in a lock leading to the Monongahela River.^[8][9]

The original plan was to connect with the C&O canal at the Monongahela River, but that canal never reached its expected western end, and the tunnel's main use was to allow overflow from the canal to enter the Monongahela.^[10] Only one or two canal boats ever went through the tunnel and lock.^[11] The tunnel was made obsolete by the arrival of the Pennsylvania Railroad in 1852.

The canal tunnel was uncovered during the construction of the U.S. Steel Tower in 1967,^[1] and later during the construction of the subway system, which used part of the tunnel on the south side.^{[citation needed]}