Description:
The opening for the Pennsylvania Canal Tunnel is on the left of the photo. The opening on the right is a Pennsylvania Railroad Tunnel. The site is currently occupied by the USX Tower.

Notes:
The canal, completed in 1834, connected Pittsburgh and Philadelphia. After crossing the Allegheny River, the canal traveled underground through most of downtown Pittsburgh. The arrival of the Pennsylvania Railroad in 1852 resulted in the demise of the canal.