Mackinac Bridge
The
Mackinac Bridge (
pronounced , like MACK-in-aw, note the silent "c", and affectionately known as the "Mighty Mac" or "Big Mac"), is a
suspension bridge spanning the
Straits of Mackinac to connect the non-contiguous
upper and
lower peninsulas of the
U.S. state of
Michigan. Envisioned since the 1880s, the bridge was completed only after many decades of struggles to begin construction. Designed by the engineer
David B. Steinman, it connects the cities of
St. Ignace on the north end with
Mackinaw City on the south.
The bridge opened on
November 1,
1957, and a year later was formally dedicated as "the world's longest suspension bridge between anchorages". This designation was chosen because the bridge would not be the world's largest using the customary way of measuring suspension bridges, the length of the center span between the towers—that title already belonged to the
Golden Gate Bridge, which has a longer center span. By saying "between anchorage", the bridge could be considered longer than the Golden Gate Bridge, and also longer than the suspended western section of the
San Francisco-Oakland Bay Bridge. (That bridge has a longer total suspension but is a double bridge with an anchorage in the middle.)
The Mackinac Bridge is still the longest two tower suspension bridge between anchorages in the western hemisphere, but it is now third longest world-wide. The combined length of the three spans of the bridge (including anchorages) is 8,614 feet (2,626 m). In 1998, the
Akashi Kaikyo Bridge in Japan became the longest with a total suspension of 12,826 feet (3,909 m).
The length of main span is 3,800 feet (1,158 m), which makes it the third largest suspension span in the
United States and tenth
largest worldwide.
Before the construction of the bridge, the typical way to cross the Straits of Mackinac was by
ferry. By the 1880s, the area had become a popular resort destination, mainly because of nearby
Mackinac Island. Year-round boat service across the straits had been abandoned as impractical because of the cold winters which would often freeze the water across the entire strait. Following the opening of the
Brooklyn Bridge in 1883, local residents began to imagine such a structure could span the straits. In 1884, a store owner in
St. Ignace published a newspaper advertisement that included a reprint of an artist's conception of the Brooklyn Bridge with the caption "Proposed bridge across the Straits of Mackinac."
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A Mackinac Island ferry passing in front of the Mackinac Bridge. |
The idea of the bridge was discussed in the Michigan Legislature as early as the 1880s. At the time the area was becoming a popular tourist destination, including the creation of
Mackinac National Park on Mackinac Island in 1875.
Despite the perceived necessity for the bridge, several decades elapsed with no formal plan. In 1920, the Michigan state highway commissioner advocated the construction of a floating tunnel across the straits. At the invitation of the legislature,
C. E. Fowler of
New York City put forth a plan for a long series of causeways and bridges across the straits from
Cheboygan, 17 miles (27 km) southeast of Mackinaw City, to St. Ignace, using
Bois Blanc,
Round, and Mackinac Island as intermediate steps.
In 1923, the state legislature ordered the State Highway Department to re-establish ferry service across the strait. By 1928, however, the service had become so expensive to operate that Governor
Fred Green ordered the department to study the feasiblity of a bridge. The department deemed the idea feasible, estimating the cost at 30 million dollars.
In 1934, the Michigan Legislature created the Mackinac Straits Bridge Authority of Michigan, to study the feasiblity of the bridge, and authorized it to sell bonds for the project. In the mid 1930s, the Authority twice attempted to obtain federal funds for the project but was unsuccessful, despite the endorsement of the
United States Army Corps of Engineers and President
Franklin D. Roosevelt. Nevertheless, between 1936 and 1940, a route was selected for the bridge and borings were made for a detailed
geological study of the route.
The project was delayed because of
World War II. The Authority was abolished by the legislature in 1947 but was reauthorized three years later in 1950. Engineers were retained in June 1950. Following a report by the engineers in January 1951, the state legistature authorized the sale of 85 million dollars in bonds construction on
April 30,
1952. A weakened bond market in 1953 forced a delay of over a year before the bonds could be issued.
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View of the bridge looking north across the Straits of Mackinac |
Engineering and construction
David B. Steinman was appointed as the design engineer in January 1953. By the end of 1953, estimates and contracts had been negotiated, and construction began on
May 7,
1954. The
American Bridge Division of
United States Steel Corporation was awarded a contract of over 44 million dollars to build the
steel superstructure. Construction took two and a half years and cost the lives of five men who worked on the bridge. It opened to traffic on schedule on
November 1,
1957, and was formally dedicated on
June 25,
1958. The bridge officially achieved its 100 millionth crossing exactly forty years after its dedication, on
June 25,
1998.
The design of the Mackinac Bridge was directly influenced by the the first
Tacoma Narrows Bridge, which failed in 1940 becasue of its instability in high winds. Three years after that disaster, Steinman had published a theoretical analysis of suspension bridge stability problems which recommended that future bridge designs include deep stiffening trusses to support the bridge deck and an open-grid roadway to reduce its wind resistance. Both of these features were incorporated into the Mackinac Bridge.
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Mackinac Bridge during a snowstorm. |
* The Mackinac Bridge is currently a
toll bridge on
Interstate 75. Prior to the coming of I-75, the bridge carried
US Highway 27.
* Every
Labor Day, two of the lanes of the bridge are closed to traffic and open to walkers for the
Mackinac Bridge Walk.
* Overall length shore to shore: 26,372 feet (8,038 m, or approximately 5 miles).
* Length from cable bent pier to cable bent pier: 7,400 feet (2,256 m).
* Total width of the roadway: 54 feet (16.5 m).:: Two outside lanes: 12 feet (3.7 m) wide each.:: Two inside lanes: 11 feet (3.4 m) wide each.:: Center mall: 2 feet (0.6 m) wide.:: Catwalk, curb and rail width: 3 feet (0.9 m) on each side.
* Width of stiffening truss in the suspended span: 68 feet (20.7 m), making it wider than the roadway it supports.
* Height of the roadway at mid-span: approximately 200 feet (61 m) above water level.
*Vertical clearance at normal temperature: :: 155 feet (47 m) at the center of the main suspension span.:: 135 feet (41 m) at the boundaries of the 3,000 foot (900 m) wide navigation channel.
*Construction cost: $99.8 million (1957 USD)
Trivia
* Travelers across the Mackinac Bridge can listen to a radio broadcast that specifically tells about the history of the bridge. One fact mentioned on the broadcast is that the painting of the bridge takes seven years, and when painting of the bridge is complete, it begins again.
* Five workers died in the construction of the bridge: three iron workers died in a catwalk collapse, one iron worker fell from the north tower, and one diver surfaced too quickly and died from "
the bends." Contrary to folklore, no bodies are buried in the concrete of the bridge.
* Since the bridge's completion, only one bridge worker has fallen to his death. David Doyle was painting when he fell 60 feet on
August 7,
1997. His body was found the next day in 95 feet of water.
* Two vehicles have gone off the bridge: a
Yugo was blown off the bridge during a particularly bad windstorm in 1989 (high speed may have also been to blame), and a sport utility vehicle drove off the bridge in 1997 (which may have been a suicide).
*The bridge is painted green and white, and at night bluish vapor lamps light up the roadway while maize-colored spotlights shine on the main towers. Michigan residents speculate that these colors symbolize the state's two largest universities since green and white are the official colors of
Michigan State University and maize and blue represent the
University of Michigan.
*
Official site*
Information and lots of photos. Many wallpaper sized images.*
Detroit News archives: The breathtaking Mackinac Bridge*
Length Comparison
