Located along the Mississippi River in East Dubuque, this tunnel runs at a sharp angle underneath the bluff above.
Built in 1867 as the railroad began approaching the Mississippi River, this tunnel runs at a 90 degree turn underneath the bluff. From here, the railroad crosses the Chicago, Burlington & Quincy (now BNSF) mainline, and into Iowa.
It is known that rock from the tunnel was used as bridge piers on the Mississippi River bridge.
The west portal of the tunnel remains as a standard rock face portal with a square design. However, the east portal was rebuilt in approximately 1899 with a new stone and concrete arch.
The tunnel was constructed using a boring and blasting method. Currently, it is still operated by Canadian National. Chicago Great Western also once operated through this tunnel.
Throughout the history of this tunnel, it has proven to be a bottleneck for railroad operations. Although not a long tunnel, the harsh curve has proven to be an issue.