Mackinac Bridge Authority

Spanning the Straits of Mackinac since 1957

Facts & Figures

The Mackinac Bridge is currently the fifth longest suspension bridge in the world.  The bridge opened to traffic on November 1, 1957.  The following facts and figures are quoted from David Steinman’s book “Miracle Bridge at Mackinac”.

LENGTHS

Total Length of Bridge (5 Miles) 26,372 Ft 8,038 Meters
Total Length of Steel Superstructure 19,243 Ft. 5,865 Meters
Length of Suspension Bridge (including Anchorages) 8,614 Ft. 8,614 Ft.
Total Length of North Approach 7,129 Ft. 2,173 Meters
Length of Main Span (between Main Towers) 3,800 Ft. 1,158 Meters

 HEIGHTS AND DEPTHS

Height of Main Towers above Water 552 Ft 168.25 Meters
Maximum Depth to Rock at Midspan Unknown Unknown
Maximum Depth of Water at Midspan 295 Ft. 90 Meters
Maximum Depth of Tower Piers below Water 210 Ft. 64 Meters
Height of Roadway above Water at Midspan 199 Ft. 61 Meters
Underclearance at Midspan for Ships 155 Ft. 47 Meters
Maximum Depth of Water at Piers 142 Ft. 43 Meters
Maximum Depth of Piers Sunk through Overburden 105 Ft. 32 Meters

CABLES

Total Length of Wire in Main Cables 42,000 Miles 67,592 km
Maximum Tension in Each Cable 16,000 Tons 14,515,995 kg
Number of Wires in Each Cable 12,580
Weight of Cables 11,840 Tons 10,741,067 kg
Diameter of Main Cables 24 1/2 Inches 62.23 cm
Diameter of Each Wire 0.196 Inches .498 cm

WEIGHTS

Total Weight of Bridge 1,024,500 Tons 929,410,766 kg
Total Weight of Concrete 931,000 Tons 844,589 kg
Total Weight of Substructure 919,100 Tons 326,931,237 kg
Total Weight of Two Anchorages 360,380 Tons 326,931,237 kg
Total Weight of Two Main Piers 318,000 Tons 288,484,747 kg
Total Weight of Superstructure 104,400 Tons 94,710,087 kg
Total Weight of Structural Steel 71,300 Tons 64,682,272 kg
Weight of Steel in Each Main Tower 6,500 Tons 5,896,701 kg
Total Weight of Cable Wire 11,840 Tons 10,741,067 kg
Total Weight of Concrete Roadway 6,660 Tons 6,041,850 kg
Total Weight of Reinforcing Steel 3,700 Tons 3,356,584 kg

RIVETS AND BOLTS

Total Number of Steel Rivets 4,851,700
Total Number of Steel Bolts 1,016,600

DESIGN AND DETAIL DRAWINGS

Total Number of Engineering Drawings 4,000
Total Number of Blueprints 85,000

MEN EMPLOYED

Total, at the Bridge Site 3,500
At Quarries, Shops, Mills, etc. 7,500
Total Number of Engineers 350

IMPORTANT DATES

Mackinac Bridge Authority Appointed June, 1950
Board of Three Engineers Retained June, 1950
Report of Board of Engineers January, 1951
Financing and Construction Authorized by Legislature April 30, 1952
D.B. Steinman Selected as Engineer  January, 1953
Preliminary Plans and Estimates Completed March, 1953
Construction Contracts Negotiated March, 1953
Bids Received for Sale of Bonds December 17, 1953
Began Construction May 7, 1954
Open to traffic  November 1, 1957
Formal dedication  June 25-28, 1958
50 millionth crossing September 25, 1984
40th Anniversary Celebration November 1, 1997
100 millionth crossing June 25, 1998