Sarnia in Lambton County, Ontario — Central Canada (North America)
The St. Clair Tunnel
⎯⎯⎯
Le Tunnel St. Clair
Photographed by Tim Boyd, May 11, 2025
1. The St. Clair Tunnel/ Le Tunnel St. Clair Marker
This was the first subaqueous tunnel in North America and one of the great engineering feats of the 19th century. Built in 1889-1891 to link the Canadian mainline of the Grand Trunk Railway with Chicago, the tunnel is 1,837 metres long with a 6-metre bore. Joseph Hobson, a Canadian engineer, designed and supervised its construction. His innovative combination of cutting shield excavation, cast iron tunnel lining, and compressed air broke the transportation bottleneck caused here and elsewhere by the impossibility of tunnelling through soft riverbeds.
Premier tunnel subaquatique en Amérique du Nord, cet ouvrage fut l'une des grandes réussites du génie du XIXe siècle. Construit en 1889-1891 pour relier la voie principale canadienne du chemin de fer du Grand Tronc à Chicago, il a 1 837 mètres de long et six mètres de diamètre. L'ingénieur canadien Joseph Hobson en conçut le plan et en supervisa le creusement, effectué à l'aide d'un bouclier d'avancement, de parois en fonte et d'air comprimé. En combinant ces moyens de manière novatrice, il mit fin à l'embouteillage causé ici et ailleurs par l'impossibilité de percer des tunnels dans les lits mous des cours d'eau.
Erected by Historic
this page online
Topics and series. This historical marker is listed in this topic list: Railroads & Streetcars. In addition, it is included in the Canada, Historic Sites and Monuments Board series list. A significant historical year for this entry is 1891.
Location. 42° 57.461′ N, 82° 24.611′ W. Marker is in Sarnia, Ontario, in Lambton County. It is at the intersection of Saint Andrew Street and Christina Street South, on the left when traveling east on Saint Andrew Street. Touch for map. Marker is at or near this postal address: 258 St Andrew Street, Sarnia ON N7T 8G8, Canada. Touch for directions.
Regionally, this marker is in the Southwest Ontario Area and in Southwestern Ontario. It is also in Central Canada. Globally, it is in North America, the Western Hemisphere, the Western World, and the Anglosphere. Historically, it finds itself in what was once a British colony, the Viceroyalty of New France, the Haudenosaunee (Iroquois) Confederacy, and Rupert’s Land.
Other nearby markers. At least 8 other markers are within 3 kilometers of this marker, measured as the crow flies: The St. Clair Tunnel
Photographed by Tim Boyd, May 11, 2025
2. The St. Clair Tunnel/ Le Tunnel St. Clair Marker
Also see . . . .
The shield method of tunnel excavation involves moving a steel shell (shield) through soft earth. Hydraulic rams force the shield along. The shield protects the tunnel heading from collapsing until a permanent lining is in place. The St. Clair Tunnel required two shields. They were the largest in the world. One started on each side of the river and they met in the middle. The tunnel was lined with cast iron and masonry. Within the shields were platforms and partitions to provide support and protect the workers.(Submitted on May 16, 2025, by Tim Boyd of Hamilton, Ontario.)
3. The St. Clair Tunnel construction technique
Lambton County Museums
Credits. This page was last revised on May 29, 2025. It was originally submitted on May 16, 2025, by Tim Boyd of Hamilton, Ontario. This page has been viewed 117 times since then and 17 times this year. Photos: 1, 2, 3. submitted on May 16, 2025, by Tim Boyd of Hamilton, Ontario. • Andrew Ruppenstein was the editor who published this page.
