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TEACH: Building the Mackinac Bridge

2 | The construction period: 1954-57

North tower. Because the bridge was in a remote area, financing the project was slow and difficult. The total cost of the project was upwards of $100 million (originally estimated at $70 million).

Construction began in 1954 and during the 42 months that followed hundreds of men worked on the various phases of the bridge construction.

The first step was to sink the large, double-walled cylinders that form the bases of the two main tower piers. These cylinders are called caissons (cay-säns). The caissons had to be sunk down into the bedrock on the lake floor, a great challenge for the divers involved.

Adding trusses and cables.When the foundation pillers were finished, the iron workers were brought in to string the massive cabling network! More than 500 workers were housed in St. Ignace, Mich., during this construction period.

A "catwalk" made of cyclone fence enabled the workers to navigate between the bridge towers, high above the lake below.

When finished, the cables were close to 25 inches in diameter. Each cable consists of 340 wires banded into a single strand; 37 strands are then assembled into a single cable. To complete the job and add extra strength, a covering is spun around each finished cable. More than 42,000 miles of wire were used in the two main bridge cables!The Mighty Mac close to completion in 1956.

The last step was to construct the road surface. The inner lane on the middle span of the bridge includes an open grid riding surface. This was installed to allow wind forces to move through the bridge.


 

Images: Erecting the north tower and adding trusses and cables, courtesy "Picture Story of the Mackinac Bridge," 1978 Voyager Press; the Mighty Mac close to completion in 1956, courtesy Albert Ballert.

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