Predecessor highways The first major overland transportation corridors in the future state of Michigan were the
Indian foot trails. One of these, the St. Joseph Trail, followed the general route of the modern I-94 across the state from the
Benton Harbor–
St. Joseph area east to the
Ann Arbor area. The
State Trunkline Highway System was created on May 13, 1913, by an act of the
Michigan Legislature; at the time, Division 6 corresponded to the rough path of today's I-94. In 1919, the
Michigan State Highway Department (MSHD) signposted the highway system for the first time, and three different highways followed sections of the modern I-94 corridor. The original
M-11 ran from the Indiana state line north to
Coloma where
M-17 connected easterly to
Detroit. The third highway was
M-19 from Detroit northeast to
Port Huron. On November 11, 1926, the
United States Numbered Highway System was approved by the
American Association of State Highway Officials (AASHO), and the original route of
US 12 replaced the highways from the state line northeasterly to Detroit;
US 31 overlapped the highway between St. Joseph and
Watervliet. The remainder of the future I-94 corridor was served by
US 25 between Detroit and Port Huron. The first span of the
Blue Water Bridge opened between Port Huron and
Point Edward, Ontario, in 1938.
Early conversions to freeways The first segments of upgraded highways along the future route of I-94 were added during
World War II. Construction on the Willow Run Expressway started in 1941 before the US entered the war. It was opened on September 12, 1942, to provide improved access to
Ford Motor Company's
Willow Run bomber plants. The
expressway was extended eastward as the Detroit Industrial Expressway into Detroit; the first section opened in 1943 and the remainder was completed in March 1945. The
interchange between the Lodge Freeway and the Edsel Ford Freeway was built in 1953 as the first full freeway-to-freeway interchange in the US. In mid-1956, the M-112 designation was decommissioned and replaced by a rerouted US 12. In other parts of the state, other segments of highway were built to bypass the cities along the future I-94 corridor. In 1940, a southern bypass of Battle Creek opened along Columbia Avenue, and the former routing through downtown on Michigan Avenue became Business US 12 (Bus. US 12). In late 1951 or early 1952, a northerly bypass of Jackson opened, and the former route through downtown on Michigan Avenue became another Bus. US 12. By the next year, the western half of the Jackson bypass opened, including a bypass of
Parma. In 1954, a new bypass of Kalamazoo and Galesburg opened; US 12 was rerouted to follow the new highway while
M-96 replaced part of the old route and US 12A in the area. The first planning maps from 1947 for what later became the
Interstate Highway System included a highway along I-94's route in Michigan. This highway was included on the 1955 plan for the "National System of Interstate and Defense Highways" with a proposed spur in the Battle Creek area. The modern I-94 was numbered I-92 between Benton Harbor–St. Joseph and Detroit with I-77 from Detroit to Port Huron in the August 1957 plans. In April 1958, the MSHD wanted to provide a single number for a more direct routing of a Detroit–Chicago freeway; the state proposed rerouting I-94 to replace I-92 in the state, but retained the I-77 designation. On June 27, 1958, AASHO adopted their original numbering plan for Michigan, minus the state's proposed changes. Around the same time, a section of
M-146 near Port Huron was converted into an approach freeway for the Blue Water Bridge.
Interstate Highway era In January 1959, officials announced that sections of US 12, the Willow Run, Detroit Industrial and Edsel Ford expressways were to be given the I-94 designation, temporarily co-designated with US 12. These sections connected Ann Arbor to Detroit, along with a bypass of Kalamazoo to Galesburg and a bypass of Jackson. Later that year, additional segments of I-94 were opened, starting with a section from Hartford to Coloma, then another from Paw Paw to Kalamazoo which connected with a segment between Galesburg to Battle Creek. The overall section from Paw Paw to Battle Creek was dedicated on December 7, 1959. In addition, a new northwest–southeast section of freeway was built east of Ypsilanti to create a more gradual curve in the routing between present-day exits 185 and 186, the original routing of the Willow Run Expressway having followed present-day Wiard Road. Signage for the state's Interstate Highways was placed on hold pending finalization of the numbering scheme, and by late 1959 that signage was being added starting with I-75 and followed by the other open segments of freeway in the state. creating the longest toll-free freeway in the country at the time. In January 1962, the US 12 designation was removed from the I-94 freeway. In the process, the designation was transferred to replace the US 112 designation in its entirety. After this transfer, I-94 was no longer concurrent with US 12, except for the Ypsilanti bypass. In 1963, the freeway was extended south of New Buffalo to end at
M-239. Traffic was diverted down M-239 into Indiana where
State Road 39 carried traffic the rest of the way to the
Indiana Toll Road. By the end of the year, a section of highway opened between Mount Clemens and Marysville, and
US 25 was rerouted to run concurrently along the freeway from the New Baltimore area northward. was installed there in 1966. The eastern terminus of I-94 in the Port Huron area was dedicated on October 14, 1964, signaling the completion of the highway between Marysville and the Blue Water Bridge. This completion displaced part of the M-146 bypass of Port Huron, the southern leg of which was retained as a connector to present-day Lapeer Road. Two years later, the gap between the Wayne–Macomb county line and the end of the freeway near Mount Clemens was filled in when another section of freeway opened. In late 1964, a plan was approved to improve the interchange with Telegraph Road (
US 24), as the original interchange did not feature access in all directions. North of
Albion, the route of the freeway previously crossed a branch of the
New York Central Railroad at-grade; the crossing was eliminated when the tracks were removed in 1968. The sections originally designated as the Willow Run Expressway were rebuilt from Rawsonville Road in
Belleville to Ozga Road in
Romulus starting in 1972. As part of this reconstruction, the segment between Haggerty and Ozga roads was widened from four to six lanes, and the eastbound lanes were realigned to facilitate construction of an interchange with
I-275, a western bypass of Detroit which was under construction at the time. The Willow Run segment was also resurfaced at this point, as the old road bed did not contain steel mesh. The final section of I-94 in Michigan opened to traffic on November 2, 1972, when the connection across the state line into Indiana was dedicated. This last segment in Michigan between M-239 and the state line opened when Indiana completed an segment of freeway in their state.
Since completion The interchange with the Southfield Freeway (
M-39) was closed entirely in 1985 to replace the original exit design, which included four on-ramps that sharply merged into the left lanes of I-94. Reconstruction added new on-ramps that merge into the freeway's right lane, while also moving the carriageways of I-94 closer together. On August 16, 1987,
Northwest Airlines Flight 255 crashed after attempting to take off from
Detroit Metropolitan Airport, killing all but one passenger upon exploding at the I-94 overpass over Middlebelt Road; that overpass was not damaged in the crash. The freeway was closed until August 18, and a memorial was later installed near the interchange between I-94 and Middlebelt Road. The completion of I-69 in the 1980s, and the approval of the
North American Free Trade Agreement, increased traffic at the Blue Water Bridge. A new toll and customs plaza was built in 1991, and, later the next year, an international task force determined that traffic on the existing structure was exceeding capacity. Environmental planning started in 1993, and construction started on the second span between Port Huron and Point Edward, Ontario in 1995. In July 1997, the second span opened. The original span was closed for rehabilitation, and both were opened to traffic in 1999. This interchange was reconfigured in 2005 to a
SPUI design that was completed in December of that year. A pair of bridges called the
Gateway Arch Bridges (alternately "Gateway to Detroit") was incorporated in the new interchange. In 2011, construction was started to widen I-94/I-69 approaching the Blue Water Bridge and to allow for dedicated local traffic and bridge traffic lanes. The lane configuration changes confused drivers in the area, especially motorists with outdated
GPS devices; because of this, MDOT installed updated signs complete with American and Canadian flags to help prevent drivers from heading to Canada by mistake. Additional construction in the Port Huron area started in late 2013 to rebuild and reconfigure the I-94/I-69 interchange outside the city. The project improved of freeway, replaced several bridges and ramps and cost $76 million (equivalent to $ in ). In June 2014, MDOT closed the ramps from I-69 eastbound to BL I-69 through the interchange until later in the year. The project was completed in September 2015. In 2016, the sections of I-94 from the Indiana state line to the
M-63 interchange was designated as part of the
West Michigan Pike Pure Michigan Byway. The West Michigan Pike originated in efforts in the 1910s to improve a highway along the western part of the Lower Peninsula of Michigan and to increase tourism along the Lake Michigan shore. The
auto trail was eventually superseded by US 12 and US 31 after the creation of the
United States Numbered Highway System in 1926. In 2020, work began on the final link of the
St. Joseph Valley Parkway to connect the US 31 freeway to I-94 east of Benton Harbor. The project cost $121.5 million and involved reconstructing the interchange with the eastern terminus of BL I-94 and of I-94 in the area. US 31 was rerouted to follow its new freeway section for from the previous end of the freeway at Napier Avenue that opened in 2003 to I-94 at BL I-94, where US 31 then followed I-94 to the I-196 interchange as before. This new routing opened on November 9, 2022. Lawmakers have not yet acted upon the department's recommendation in the proposal. Construction began on August 7, 2023, on a privately funded MDOT pilot project to upgrade the left lane for
connected and
autonomous vehicles between Ann Arbor and Detroit. ==Memorial highway names==