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International Bridge

Sault Ste. Marie International Bridge

International Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: May 16, 2006, June 25, 2011, and September 6, 2014

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Key Facts

Facility Carried / Feature Intersected
I-75 / TC-17B Over St. Marys River and Associated Canal System
Sault Ste. Marie: Chippewa County, Michigan and Algoma District, Ontario: Canada and United States
Structure Type
Metal Cantilever (Arch and Suspended Deck) Bolt-Connected Warren Through Truss, Fixed and Approach Spans: Metal 8 Panel Bolt-Connected Warren Deck Truss, Fixed
Construction Date and Builder / Engineer
1962 By Builder/Contractor: Unknown and Engineer/Design: Steinman, Boynton, Gronquist and London of New York, New York

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
430 Feet (131.1 Meters)
Structure Length
9,281 Feet (2828.7 Meters)
Roadway Width
28 Feet (8.53 Meters)
7 Main Span(s) and 56 Approach Span(s)
NBI Number

Historic Significance Rating (HSR)
View Information About HSR Ratings

Bridge Documentation

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

View Michigan Department of Transportation Official Website For This Bridge

View The International Bridge Administration Website

Although perhaps the most well-known and visible bridge in Sault Ste Marie, from a historical perspective, this is the least significant of the bridges, when compared to the International Railroad Bridge, and the Emergency Swing Span, and the Ashmun Street Bridge

This bridge is a complex structure. The minor spans are all deck plate girder spans. There is a deck truss span over the Power Canal on the Michigan side. The span over the U.S. canals is a two-span through arch. The span over the Ontario canal is a single span through arch. The bridge is noted for its sag in between these two through arch spans, which was done because under-bridge clearance was not a concern at that part and so to reduce costs, the piers were built with a lower height there. The International Bridge lacks any v-lacing or lattice, and all connections are bolted. There are rivets on the built-up beams however. The concrete piers are tall and impressive, but feature minimal aesthetics, especially when compared to a bridge like the Blue Water Bridge.

Information and Findings From Michigan Historic Bridge Inventory

Narrative Description

MDOT Historic Bridge Chippewa County I-75 St. Mary's River

This is one of Michigan's five monumental bridges.  The twin cities of Sault Ste. Marie in Michigan and Ontario were linked by a railroad bridge in 1887, but automobile traffic between the cities was carried by ferry until this bridge was opened in 1962. An International Bridge Authority was created by the Michigan State Legislature and passed before construction was begun.

It was designed by the firm of Steinman, Boyton, Gronquist, and London of New York and cost twenty million dollars. This bridge was an ambitious project because it crossed two navigation canals and the St. Mary's River.Overall, the bridge is 2.76 miles long, including approaches, and provides a two lane roadway 28 feet wide. The Main spans had to be erected without the use of falsework so as not to obstruct traffic through the American and Canadian Locks. This was done through the balanced addition of steel structural members on the main spans.


Photo Galleries and Videos: International Bridge

View Photo Gallery
2014 Bridge Photo-Documentation
Original / Full Size Photos
A collection of overview and detail photos. This gallery offers photos in the highest available resolution and file size in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer
View Photo Gallery
2014 Bridge Photo-Documentation
Mobile Optimized Photos
A collection of overview and detail photos. This gallery features data-friendly, fast-loading photos in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer
View Photo Gallery
Pre-2014 Bridge Photo-Documentation
A collection of overview and detail photos. This photo gallery contains a combination of Original Size photos and Mobile Optimized photos in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer


Maps and Links: International Bridge

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