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International Bridge


International Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: May 16, 2006
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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
Structure Type
Metal Cantilever (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 Meters)
Structure Length
9280.6 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)

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 RiverThis 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.


Photos and Videos: International Bridge

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Bridge Photo-Documentation
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