Макинакский мост: Символ Мичигана

Suspension bridge in Michigan, US

The Mackinac Bridge ('/m//æ//k//ə//n//ɔː/ MAKənaw; also referred to as the Mighty Mac or Big Mac) is a suspension bridge that connects the Upper and Lower peninsulas of the U. S. state of Michigan. It spans the Straits of Mackinac, a body of water connecting Lake Michigan and Lake Huron, two of the Great Lakes. Opened in 1957, the 26372 feet (8038 m) The bridge has since become an iconic symbol of the state of Michigan.

The bridge opened on November 1, 1957, connecting two peninsulas linked for decades by ferries. At the time, the bridge was formally dedicated as the "world's longest suspension bridge between anchorages", allowing a superlative comparison to the Golden Gate Bridge, which has a longer center span between towers, and the San Francisco–Oakland Bay Bridge, which has an anchorage in the middle. It remains the longest suspension bridge with two towers between anchorages in the Western Hemisphere. Much longer anchorage to anchorage spans have been built in the Eastern Hemisphere, including the Akashi Kaikyō Bridge in Japan (6532 feet (1991 m)), but the long leadups to the anchorages on the Mackinac make its total shoreline to shoreline length of 26,372 feet — 28 feet short of 5 mile (8 km) — longer than the Akashi Kaikyo (2.4 mile (4 km)). The length of the bridge's main span is 3800 feet (1158 m), which makes it the third longest suspension span in the United States and 27th longest suspension span worldwide. It is also one of the world's longest bridges overall.

The Algonquian peoples who lived in the straits area prior to the arrival of Europeans in the 17th century called this region Michilimackinac, which is widely understood to mean Place of the Great Turtle. This is thought to refer to the shape of what is now called Mackinac Island. This interpretation of the word is debated by scholars. Trading posts at the Straits of Mackinac attracted peak populations during the summer trading season; they also developed as intertribal meeting places. As usage of the state's mineral and timber resources increased during the 19th century, the area became an important transport hub. In 1881 the three railroads that reached the Straits, the Michigan Central, Grand Rapids & Indiana, and the Detroit, Mackinac & Marquette, jointly established the Mackinac Transportation Company to operate a railroad car ferry service across the straits and connect the two peninsulas. Improved highways along the eastern shores of the Lower Peninsula brought increased automobile traffic to the Straits region starting in the 1910s. The state of Michigan initiated an automobile ferry service between Mackinaw City and St. Ignace in 1923; it eventually operated nine ferry boats that would carry as many as 9,000 vehicles per day. Traffic backups could stretch as long as 16 mile (26 km).

After the opening of the Brooklyn Bridge in 1883, local residents began to imagine that 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". The idea of the bridge was discussed in the Michigan Legislature as early as the 1880s. At the time, the Straits of Mackinac area was becoming a popular tourist destination, especially following the creation of Mackinac National Park on Mackinac Island in 1875. At a July 1888 meeting of the board of directors of the Grand Hotel on Mackinac Island, Cornelius Vanderbilt II proposed that a bridge be built across the straits, of a design similar to the one then under construction across the Firth of Forth in Scotland. This would advance commerce in the region and help lengthen the resort season of the hotel.

In 1923, the state legislature ordered the State Highway Department to establish ferry service across the strait. More and more people used ferries to cross the straits each year, and as they did, the movement to build a bridge increased. Chase Osborn, a former governor, wrote:

Michigan is unifying itself, and a magnificent new route through Michigan to Lake Superior and the Northwest United States is developing, via the Straits of Mackinac. It cannot continue to grow as it ought with clumsy and inadequate ferries for any portion of the year. By 1928, the ferry service had become so popular and so expensive to operate that Governor Fred W. Green ordered the department to study the feasibility of building a bridge across the strait. The department deemed the idea feasible, estimating the cost at $30 million (equivalent to $ in ). In 1934, the Michigan Legislature created the Mackinac Straits Bridge Authority to explore possible methods of constructing and funding the proposed bridge. The Legislature authorized the Authority to seek financing for the project. In the mid 1930s, during the Great Depression, when numerous infrastructure projects received federal aid, the Authority twice attempted to obtain federal funds for the project but was unsuccessful. The United States Army Corps of Engineers and President Franklin D. Roosevelt endorsed the project but Congress never appropriated funds. Between 1936 and 1940, the Authority selected a route for the bridge based on preliminary studies. Borings were made for a detailed geological study of the route. The preliminary plans for the bridge featured a three lane roadway, a railroad crossing on the underdeck of the span, and a center anchorage double suspension bridge configuration similar to the design of the San Francisco – Oakland Bay Bridge. Because this would have required sinking an anchorage pier in the deepest area of the Straits, the practicality of this design may have been questionable. A concrete causeway, approximately 4000 feet (1219 m), extending from the northern shore, was constructed in shallow water from 1939 to 1941. However, a unique engineering challenge was created by the tremendous forces that operate against the base of the bridge, because the lakes freeze during the winter, causing large icebergs to place enormous stress on the bridge. At that time, with funding for the project still uncertain, further work was put on hold because of the outbreak of World War II. The Mackinac Straits Bridge Authority was abolished by the state legislature in 1947, but the same body created a new Mackinac Bridge Authority three years later in 1950. In June 1950, engineers were retained for the project. By then, it was reported that cars queuing for the ferry at Mackinaw City did not reach St. Ignace until five hours later, and the typical capacity of 460 vehicles per hour could not match the estimated 1,600 for a bridge. After a report by the engineers in January 1951, the state legislature authorized the sale of $85 million (equivalent to $ in ) in bonds for bridge construction on April 30, 1952. However, a weak bond market in 1953 forced a delay of more than a year before the bonds could be issued.

David B. Steinman was appointed as the design engineer in January 1953 and by the end of 1953, estimates and contracts had been negotiated. A civil engineer at the firm, Abul Hasnat, did the preliminary plans for the bridge. Total cost estimate at that time was $95 million (equivalent to $ in ) with estimated completion by November 1, 1956. Tolls collected were to pay for the bridge in 20 years. Construction began on May 7, 1954. The bridge was built under two major contracts. The Merritt Chapman and Scott Corporation of New York was awarded the contract for all major substructure work for $25.7 million (equivalent to $ in ), while the American Bridge Division of United States Steel Corporation was awarded a contract of more than $44 million (equivalent to $ in ) to build the steel superstructure. Construction, staged using the 1939–41 causeway, took three and a half years (four summers, no winter construction) at a total cost of $100 million and the lives of five workers. Contrary to popular belief, none of them are entombed in the bridge. It opened to traffic on schedule on November 1, 1957, and the ferry service ceased on the same day. The bridge was formally dedicated on June 25, 1958. G. Mennen Williams was governor during the construction of the Mackinac Bridge. He began the tradition of the governor leading the Mackinac Bridge Walk across it every Labor Day. Senator Prentiss M. Brown has been called the "father of the Mackinac Bridge", and was honored with a special memorial bridge token created by the Mackinac Bridge Authority. The bridge officially achieved its 100 millionth crossing exactly 40 years after its dedication, on June 25, 1998.

The design of the Mackinac Bridge was directly influenced by the lessons from the first Tacoma Narrows Bridge, which failed in 1940 because 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 design of the Mackinac Bridge. The stiffening truss is open to reduce wind resistance. The road deck is shaped as an airfoil to provide lift in a cross wind, and the center two lanes are open grid to allow vertical (upward) air flow, which fairly precisely cancels the lift, making the roadway stable in design in winds of up to .

Some individuals have difficulty crossing bridges, a phenomenon known as gephyrophobia. The Mackinac Bridge Authority has a Drivers Assistance Program that provides drivers for those with gephyrophobia, or anyone who is more comfortable having someone else drive them across. More than a thousand people use this service every year. Those interested can arrange, either by phone or with the toll collector, to have their cars or motorcycles driven to the other end. There is an additional fee for this service. Bicycles and pedestrians are not permitted on the bridge. Up until 2017, an exception was allowed for riders of two annual bicycle tours. As of March 13, 2020, a program to transport bicycles has been suspended indefinitely due to the COVID 19 pandemic. A yearly exception is also made for pedestrians, see "Bridge Walk" below. Travelers across the Mackinac Bridge can listen to an AM radio broadcast that recounts the history of the bridge and provides updates on driving conditions.

The first Mackinac Bridge Walk was held in 1958, when it was led by Governor G. Mennen Williams. The first walk was held during the Bridge's Dedication Ceremony held in late June, and has been held on Labor Day since 1959. Until 2018, school buses from local districts transported walkers from Mackinaw City to St. Ignace to begin the walk. Thousands of people, traditionally led by the governor of Michigan, cross the five mile (8 km) span on foot from St. Ignace to Mackinaw City. Before 1964, people walked the Bridge from Mackinaw City to St. Ignace. Prior to 2017, two lanes of the bridge would remain open to public vehicle traffic; this policy was changed in 2017 to close the entire bridge to public vehicle traffic for the duration of the event. The Bridge Walk is the only day of the year that hikers can hike this section of the North Country National Scenic Trail.

During the summer months, the Upper Peninsula and the Mackinac Bridge have become a major tourist destination. In addition to visitors to Mackinac Island, the bridge has attracted interest from a diverse group of tourists including bridge enthusiasts, bird watchers, and photographers. The Straits area is a popular sailing destination for boats of all types, which make it easier to get a closer view to the underlying structure of the bridge.

On June 25, 1958, to coincide with that year's celebration of the November 1957 opening, the United States Postal Service (USPS) released a 3¢ commemorative stamp featuring the recently completed bridge. It was entitled "Connecting the Peninsulas of Michigan" and 107,195,200 copies were issued. The USPS again honored the Mackinac Bridge as the subject of its 2010 priority mail $4.90 stamp, which went on sale February 3. The bridge authority and MDOT unveiled the stamp, which featured a "seagull's eye view" of the landmark, with a passing freighter below. Artist Dan Cosgrove worked from panoramic photographs to create the artwork. This is one of several designs that Cosgrove has produced for the USPS. On April 24, 1959, Captain John S. Lappo, an officer in the Strategic Air Command, operating from Lockbourne AFB flew his Boeing B 47 Stratojet beneath the bridge. Following a general court martial, he was grounded for life. A feature length documentary entitled Building the Mighty Mac was produced by Hollywood filmmaker Mark Howell in 1997 and was shown on PBS. The program features numerous interviews with the key people who built the structure and includes restored 16mm color footage of the bridge's construction. The history and building of the bridge was featured in a 2003 episode of the History Channel TV show Modern Marvels. On July 19, 2007, the Detroit Science Center unveiled an 80 feet (24 m), 19 feet (6 m) scale model of the Mackinac Bridge. The exhibit was part of the state's 50th anniversary celebration of the bridge. Sherwin Williams supplied authentic Mackinac Bridge colored paint for the project. The bridge and its maintenance crew were featured in an episode of the Discovery Channel TV show Dirty Jobs on August 7, 2007. Host Mike Rowe and crew spent several days filming the episode in May 2007. MDOT also featured the bridge on the cover of the 2007 state highway map to celebrate its 50th anniversary.