Interstate 75 (I-75) is part of the Interstate Highway System. It starts near Hialeah and Miami Lakes and ends at the Canadian border in Sault Ste. Marie, Michigan. I-75 enters the state from Ohio, just north of Toledo, and travels mostly north through Detroit, Flint, and Bay City. It crosses the Mackinac Bridge and ends at the border in Sault Ste. Marie. The highway is about 396 miles (637 km) long and runs on both of Michigan's major peninsulas. The areas I-75 passes through include farmland in southern Michigan, forests in the north, suburban areas where people live and work, and the city of Detroit. The highway also crosses major bodies of water using three important bridges. There are four auxiliary highways and nine current or former business routes connected to I-75, which are labeled as Business Loop I-75 (BL I-75) or Business Spur I-75 (BS I-75).

I-75 has several names. The southern part was called the Detroit–Toledo Expressway during planning in the 1950s and 1960s. In Detroit, it is known as the Fisher Freeway or the Walter P. Chrysler Freeway, named after people who helped develop the automobile industry. Sections near the Mackinac Bridge are called the G. Mennen Williams Freeway or the Prentiss M. Brown Freeway, named after leaders who supported building the bridge. Officially, the entire highway is called the American Legion Memorial Highway, named after the American Legion organization. Some parts of I-75 are also part of the four Great Lakes Circle Tours in Michigan.

Before Michigan became a state, many Native American trails were used along the path of I-75. After statehood, some of these trails became plank roads, which later became some of the first state highways. In the 1920s, five of these roads were added to the United States Numbered Highway System: US Highway 2 (US 2), US 10, US 24, US 25, and US 27. In the 1950s, a Michigan Turnpike was planned as a toll road with limited access in the Lower Peninsula. However, after the Federal Highway Act of 1956 was passed, the turnpike idea was stopped, and a free Interstate Highway was built instead. Construction began in 1957, signs were placed in 1959, and I-75 was completed in 1973. Since then, improvements have been made, including the Zilwaukee Bridge near Saginaw and better connections to the Ambassador Bridge in Detroit.

Route description

I-75 is known as "Michigan's Main Street" and is part of the National Highway System (NHS), a network of roads important to the country's economy, defense, and movement of people and goods. It is the busiest highway in Michigan. In 2010, about 194,300 vehicles used the highway each day between M-8 (Davison Highway) and McNichols Road in Detroit. In contrast, the lowest traffic was 3,208 vehicles between the M-48 and M-80 interchanges in Chippewa County. I-75 carries parts of all four Great Lakes Circle Tours in the state. It is the only highway in Michigan that runs on both the Upper and Lower Peninsulas (UP and LP). Between the Ohio state line and Kawkawlin, I-75 has between six and ten lanes total; other sections have four to six lanes.

I-75 enters Michigan in Monroe County, crossing the Ohio state line north of Toledo. It carries the Lake Erie Circle Tour (LECT) near the North Maumee Bay of Lake Erie and runs parallel to the shoreline, passing the community of Luna Pier. Further north, it passes to the southeast of Monroe and crosses the River Raisin between the city and the river mouth. North of the river, the highway moves inland through farmland. Near Newport, I-275 splits off to the northwest, and I-75 continues northeast through Monroe County. When it crosses the Huron River, the highway enters Wayne County between South Rockwood and Rockwood.

On the north side of the county line, I-75 runs inland and parallel to the Detroit River, entering the Downriver area. The highway turns northerly after the interchange with M-85 (Fort Street) near Gibraltar, and the LECT departs I-75 to follow M-85 north of the interchange. The landscape changes to suburban residential areas instead of farmland. The highway turns back northeasterly in Taylor and intersects the southern end of M-39 (Southfield Highway) in Lincoln Park. I-75 crosses the Ecorse River and passes through an industrial area of Metro Detroit. Farther north, the highway spans the River Rouge in the southern part of Detroit.

I-75 runs parallel to M-85 (Fort Street) and follows the Detroit River as far east as the Ambassador Bridge. Near the bridge, the highway turns 90° away from the river and intersects the eastern end of I-96 before turning again to follow the river inland. From there, I-75 meets M-10 (Lodge Freeway) and M-5 (Grand River Avenue). East of Grand River, I-75 passes Little Caesars Arena, home of the Detroit Red Wings and Detroit Pistons, and passes under M-1 (Woodward Avenue). East of Woodward, the highway travels past Comerica Park and Ford Field, homes of the Detroit Tigers and Detroit Lions, respectively.

Immediately east of Ford Field, I-75 turns northwesterly to follow the Chrysler Freeway away from downtown Detroit. The transition from the Fisher Freeway involves one-lane ramps at the interchange with connections to I-375 and M-3 (Gratiot Avenue). Heading north-northwesterly, I-75 passes east of Wayne State University and through an interchange with I-94 (Edsel Ford Freeway). The Chrysler Freeway runs west of Hamtramck and east of Highland Park, both enclaves within Detroit. I-75 meets M-8 (Davison Freeway) and continues through residential areas of Detroit's northern side. North of M-102 (8 Mile Road), the highway exits Detroit and enters Oakland County. The Chrysler Freeway passes through Hazel Park, a location known as the "worst freeway for accidents in Metro Detroit" near a curve on 9 Mile Road.

Further north, I-75 intersects I-696 near 10 Mile Road. The highway continues northward for about six miles (9.7 km) into Troy, where it turns westward. The route zigzags through Troy and Auburn Hills, alternating directions to bypass Pontiac. Near the M-59 interchange, I-75 passes Chrysler's headquarters. Farther north, by the M-24 interchange, it runs near the former site of The Palace of Auburn Hills. The highway travels through suburban residential areas as it moves northwesterly away from Pontiac. These subdivisions end north of Clarkston, the location of the northern terminus for US 24. Continuing through Holly and Newark, the highway transitions to a rural, wooded setting and enters Genesee County.

As I-75 approaches Grand Blanc, the landscape changes back to suburbs. I-475 (UAW Freeway) splits off to the north to bypass Flint's east side, and I-75 merges with US 23. The combined I-75/US 23 turns northerly to round the west side of Flint. I-75/US 23 meets I-69 near Bishop International Airport southwest of downtown Flint. The highway continues northward along western residential neighborhoods, encountering the northern end of I-475 near Mount Morris. I-75 passes west of Clio and east of Birch Run, home to a large outlet mall. From there, the highway travels through farmland in southern Saginaw County.

I-75/US 23 enters the southern reaches of the suburban Tri-Cities at Bridgeport and proceeds northward. The highway passes east of downtown Saginaw. I-675 splits off to run westward into downtown, and I-75 curves around to the northwest to cross the Saginaw River on the Zilwaukee Bridge in Zilwaukee. North of the river, I-675 reconnects to I-75, which continues northward into Bay County. The highway passes west of Bay City, encountering the interchange marking the eastern end of US 10 and the western end of M-25. From there, I-75/US 23 curves northwesterly to bypass Kawkawlin before continuing north to the Standish area through farmlands inland from Saginaw Bay. West of Standish, US 23 splits to follow the Lake Huron shoreline, and I-75 turns northwesterly to run inland.

West of Sterling, the landscape changes to forest lands. I-75 continues northwestward through Arenac County and crosses into western Ogemaw County. M-30 passes under the highway without an interchange as I-75 rounds the west side of West Branch. On the northwest side of the city, M-55 merges onto I-75, and the two highways run concurrently westward into Roscommon County. East of Prudenville, M-55 splits from the highway. I-75 turns northward to curve around the east of Houghton and Higgins lakes. Turning back to the northwest, the highway bypasses Roscommon to the south and enters southern Crawford County. About five miles (8.0 km) north of the county line, I-75 meets the northern end of US 127, the former US 27.

After the US 127 interchange,

History

Before Michigan became a state, the first roads were Indian trails. The French-Indian Trail passed through southeastern Michigan, connecting Toledo, Monroe, and Detroit. The Saginaw Trail ran north from Detroit to Saginaw, where it linked with the Mackinaw Trail. This trail ran roughly parallel to and west of today’s I-75. Another path, the Cheboygan Trail, ran parallel to the modern freeway to the east, connecting the West Branch area to Cheboygan. In the Upper Peninsula, an extension of the Mackinac Trail connected St. Ignace and Sault Ste. Marie. In the 19th century, the Michigan Legislature allowed private companies to build and operate plank roads or turnpikes. These roads replaced many Indian trails. Early roads were made of oak planks, but later laws allowed gravel to be used instead. By the early 1900s, only 23 of the 202 planned turnpikes remained in use. Many companies that received permission to build roads never completed them. The remaining plank roads were later taken over by the state or bought by railway companies.

The State Trunkline Highway System was created on May 13, 1913. Parts of this system were built along the future route of I-75. Division 1 connected the Ohio state line to Detroit, and Division 2 linked Detroit to Mackinaw City. A branch of Division 7 ran from St. Ignace to Sault Ste. Marie. The system was marked with signs in 1919, and maps showed these highways for the first time. The first M-10 was built along the route from Ohio through Detroit to Standish. M-76 connected Standish to Grayling, where M-14 ran north to Cheboygan. From there, M-10 continued to Mackinaw City. In the Upper Peninsula, M-12 connected St. Ignace to Sault Ste. Marie along a route east of the old Mackinac Trail. When the United States Numbered Highway System was created on November 11, 1926, most of these highways were renamed as part of the national system. From the state line north, M-10 became part of US 24 and US 25. At Detroit, M-10 was part of US 10. North of Grayling, M-14 became part of US 27. M-12 was used for US 2.

In 1933, the Michigan State Highway Department (MSHD) changed the route of US 2 between Rogers Park and Sault Ste. Marie. The new route followed the Mackinac Trail instead of going east to Cedarville and north to Sault Ste. Marie. The old route was renamed M-121.

By 1945, a divided highway called Alternate US 24 (US 24A) opened from the state line to Erie. After World War II, the MSHD planned to convert some highways into freeways. In 1947 maps, the future I-75 route was included in plans for the Interstate Highway System. This route was also part of the General Location of National System of Interstate Highways released in 1955 as the federal government prepared for the freeway system.

In 1951, the Michigan Turnpike Authority (MTA) was created. The MTA proposed building a toll freeway that would run north to south across the state. The original plan had the turnpike start at Bridgeport and end at Rockwood. At the time, the state highway commissioner, Charles Ziegler, did not support the MTA and tried to delay its progress. Ziegler, who was on the MTA board, publicly disagreed with the authority’s chairman, George Higgins, and said the MSHD would build a parallel freeway that would reduce tolls by 40 to 50 percent. Trucking groups in the state also opposed the tolls, preferring a small increase in gas taxes instead. Detroit refused to allow the MTA to build a turnpike through the city due to issues involving the River Rouge, Rouge Park, and access rights. In 1955, the Michigan Supreme Court ruled in favor of the MTA, allowing it to sell bonds for its Bridgeport–Rockwood and Detroit–Chicago toll roads.

Early planning maps showed the first turnpike running west of Detroit, near US 24 (Telegraph Road). This route later became part of I-75, with I-275 planned to loop into downtown Detroit. By December 1955, the proposed length of the Michigan Turnpike was extended to run from the Ohio state line through Detroit, Saginaw, and to the southern end of the Mackinac Bridge. However, by April 1956, plans for extensions and an east-west companion road were canceled. In January 1956, the MTA proposed a state constitutional amendment to allow the legislature to issue state-guaranteed bonds for construction. However, the MSHD opposed the MTA, which hurt its ability to get funding. When the Federal Aid Highway Act of 1956 was approved, Ziegler and the MSHD announced plans to build a full freeway across the state, which reduced support for the Michigan Turnpike. By August 1956, the MTA reduced its staff but continued planning to sell bonds for construction. Financiers said the sale would only work if the turnpike had no competition. In 1958, the Michigan Townships Association called for the MTA to be abolished, but the legislature did not act on the request until 1962, when it repealed the law that created the MTA.

The first parts of I-75 opened in 1957, starting with the section near the Ohio state line in October 1957. The Mackinac Bridge opened on November 1, 1957. A new highway and interchange connected US 2 to the bridge on the north end and to US 27 and US 31 on the south end. In 1958, the MSHD officially proposed the I-75 number. On June 30, 1958, the first part of the "Fenton–Clio Expressway" opened. Construction on the Chrysler Freeway in Detroit began on January 30, 1959. In October 1959, I-75 signs were placed along the Detroit–Toledo Expressway, replacing US 24A signs in Monroe after final approval of the numbering system.

In November 1960, sections of I-75 opened from Indian River to the southern end of the Mackinac Bridge in Mackinaw City and from St. Ignace to Evergreen Shores. By December 1960, the section between Evergreen Sh

Freeway names

Interstate 75 (I-75) has six named sections in Michigan. The southernmost part, from the state line to the Detroit area, is called the Detroit–Toledo Expressway. The segment through southern and central Detroit is named the Fisher Freeway. This section was dedicated on September 17, 1970, to honor the Fisher Brothers, who founded Fisher Body, a company later part of General Motors. After passing through downtown Detroit, I-75 continues north along the Walter P. Chrysler Freeway. This name honors Walter P. Chrysler, founder of Chrysler. The Detroit Common Council chose this name on November 6, 1957, and it was made official by state law in 1990. The state defines the northern end of this segment at the Oakland–Genesee county line.

The entire length of I-75 in Michigan is officially called the American Legion Memorial Highway. However, this name is rarely used on the southernmost parts of the highway. The American Legion received this designation in 1969 through state law, which required private groups to pay for the signs. In 1984, Public Act 174 changed the name again to honor the American Legion and assigned responsibility for the signs to the Michigan Department of Transportation (MDOT). Another name, the Michigan Bicentennial Freedom Way, was applied to I-75 in 1976 through Senate Concurrent Resolution 216. This name was only used for one year and was officially removed in 2001.

Two other sections near the Straits of Mackinac were named in 1976 to honor people important to the construction of the Mackinac Bridge. From the Cheboygan–Otsego county line to the bridge, I-75 is called the G. Mennen Williams Freeway. This name honors G. Mennen Williams, a former governor once called "Michigan's Politician of the Century" by the press. The section in Mackinac County, from the northern end of the Mackinac Bridge, is named the Prentiss M. Brown Freeway. This honors Prentiss M. Brown, a former congressman and senator who served on the Mackinac Bridge Authority board until his death in 1971.

Monumental bridges

Along its route in the state, I-75 crosses three of Michigan's large bridges. The first is the Zilwaukee Bridge near Saginaw. The original bridge over the Saginaw River at Zilwaukee was built in 1960 as a type of bridge that can open for ships. When the bridge opened for ships, traffic on I-75/US 10/US 23 was often delayed for up to four hours on busy weekends. A new bridge was approved in 1974, and construction began in October 1979. A major accident in August 1982 delayed the project. A section of the new bridge partially collapsed when workers added too much weight to an area under construction. The 300-foot (91 m) section tilted, with one end 3 feet (0.91 m) higher and the other 5 feet (1.5 m) lower. The bridge was originally expected to cost $76.8 million and finish in 1983. It cost $131.3 million (equivalent to $346 million in 2024) and opened on September 19, 1988. This bridge is the largest concrete segmental bridge in the United States.

The second bridge is the Mackinac Bridge, which connects Michigan's two peninsulas at the Straits of Mackinac. A plan for a bridge was first proposed in 1888 by a director of the Grand Hotel on Mackinac Island. Ferry service across the straits began in 1923, and a bridge authority was created in 1934 to study a permanent connection. This group first considered a plan in 1921 for a series of bridges connecting Cheboygan to St. Ignace through several islands. The federal Public Works Administration rejected funding requests for this project. A new plan for a direct bridge was later proposed, based on designs from the Tacoma Narrows Bridge. The collapse of that bridge and World War II delayed progress. Tests of the lake bottom and a 4,200-foot-long (1,300 m) causeway on the St. Ignace side were completed, but no further work began until 1950.

The Mackinac Bridge Authority (MBA) was created in 1952 to sell bonds to fund the bridge. Bonds were sold on December 17, 1953, to cover the $99.8 million (equivalent to $932 million in 2024) cost. The bridge was designed by David B. Steinman and built by Merritt-Chapman & Scott and the American Bridge Company. Construction began in 1954, and the Mackinac Bridge opened to traffic on November 1, 1957. Final work was completed in September 1958. The bridge has a 3,800-foot (1,200 m) central suspension span, with two 1,800-foot (550 m) side spans. Including the backstay spans, the bridge is 8,614 feet (2,626 m) long between anchor points, the longest in the world when it opened. The total length is 26,444 feet (8,060 m), with two 555-foot-tall (169 m) towers and 155 feet (47 m) of space for ships under the main span. In 2000, the bridge was named "Michigan's No. 1 Civil Engineering Project of the 20th Century" by the Michigan Section of the American Society of Civil Engineers (ASCE). It was also named a National Historic Civil Engineering Landmark in 2010 by the national ASCE.

The northernmost of the three bridges is the International Bridge, connecting Sault Ste. Marie in Michigan and Ontario. Governments on both sides of the border formed a bridge authority in 1935 to build the bridge. Construction began on September 16, 1960. The International Bridge is nearly three miles (4.8 km) long, crossing the American and Canadian navigation channels for the Soo Locks and the St. Marys River. The American approach is 2,471 feet (753 m), and the Canadian approach is 2,942 feet (897 m). The center span over the river is 9,280 feet (2,830 m), with 1,260-foot (380 m) and 830-foot (250 m) spans over the American and Canadian shipping channels. The same firm that designed the Mackinac Bridge built this bridge for $20 million (equivalent to $158 million in 2024). It opened to traffic on October 31, 1962.

Related trunklines

In Michigan, there are four supporting Interstate Highways connected to I-75. I-275 starts as a loop in northern Monroe County and connects to I-96 and I-696. This highway serves areas in western Wayne County and the Detroit Metropolitan Wayne County Airport. Originally, it was planned to link to I-75 north of Pontiac. I-375 was the shortest signed Interstate in the United States and connects to downtown Detroit. I-475 is called the UAW Freeway and the David Dunbar Buick Freeway. It runs through Flint’s downtown area, parallel to I-75 on the city’s west side. The fourth supporting Interstate is I-675, a loop into Saginaw that provided an alternate route for I-75 when a drawbridge over the Saginaw River was still in use.

In addition to these highways, there are eight business routes in Michigan that connect to I-75. These routes link to the downtown areas of Pontiac, Bay City, West Branch, Roscommon, Grayling, Gaylord, St. Ignace, and Sault Ste. Marie. A ninth route was once designated in Saginaw, and a 10th route has been proposed for Indian River.