Early history {{multiple image Before Michigan became a state, the first land transportation corridors were the
Indian trails. The original Shore Trail ran roughly parallel to the route of the modern-day US 23 from the
Bay City area to Cheboygan. Another section of the current highway followed the
Saginaw Trail between Flint and Saginaw. Later, during the
auto trail era, the modern-day US 23 also coincided with the east branch of the
Dixie Highway and part of the Lower Peninsula section of the
Theodore Roosevelt International Highway. The Dixie Highway was created by William S. Gilbreath after he developed the
Lincoln Highway. The highway was designed to link the Great Lakes with the
Gulf of Mexico, and to commemorate a half century of peace between the North and the South after the
American Civil War. At the urging of Governor
Woodbridge N. Ferris, the northern terminus was located at the Straits of Mackinac. The highway had two branches in the Lower Peninsula; the eastern branch followed what later became US 23 north of Standish. The Theodore Roosevelt International Highway was named for former US president
Theodore Roosevelt after his death in 1919. Overall, this highway ran from
Portland, Oregon, to
Portland, Maine, by way of Michigan and the Canadian province of
Ontario. In Michigan, it also followed US 23 north of Standish. The highway was also part of the East Michigan Pike, designed to be a counterpart of the West Michigan Pike on the other side of the Lower Peninsula. The original route of the East Michigan Pike included a section along the coast of
The Thumb between Bay City and
Port Huron and used the same route as the Dixie Highway north of Bay City. Backers of this auto trail lost out in terms of name recognition to the Dixie Highway, relegating the East Michigan Pike to the list of failed auto trails. The southern part of what is now US 23 in the state was also part of the auto trail craze. The Top of Michigan Trail was designated in 1917 from the state line north to the Bay City area, before turning inland along other roadways. The name faded from shortly after the time the
Michigan State Highway Department (MSHD) assigned the first highway numbers in the state. The first state highways along the US 23 corridor were numbered
M-65 from the Ohio line north to the Flint area and
M-10 from Flint north to Mackinaw City by July 1, 1919. When originally designated, M-65 was in two sections: the southern segment ran from the Ohio state line north to the Dundee area; the northern section ran between Ann Arbor and Flint by way of Brighton and Fenton.
United States Numbered Highways US 23 was commissioned on November 11, 1926, with the debut of the United States Numbered Highway System. The MSHD removed the M-10 and M-65 designations from the highway at the time. As it was originally designated, US 23 crossed into Michigan from Ohio south of
Temperance and ran north to
Ypsilanti via
Ida and
Maybee. Once the highway entered Ann Arbor, it followed the roads that preceded the modern-day freeway up to Flint. From Flint to Saginaw, US 23 ran concurrently with US 10. On the way north to Bay City, the highway ran on the west side of the Saginaw River before turning north to the Standish area. From Standish to Mackinaw City, US 23 initially took a more inland route through the northeastern Lower Peninsula. Starting in 1929, MSHD started updating the route that US 23 followed through the Lower Peninsula. Late that year, the routing was moved to the east side of the Saginaw River, and
M-47 was extended along the former course on the west side of the river. During 1930, a set of changes realigned the highway's route through the southeast corner of the state. Near
Ida, US 23 was rerouted along M-50 to Dundee and north through Milan to Ann Arbor, bypassing Maybee and
Whittaker. US 23 was moved from its inland routing between Omer and Tawas City via
Whittemore to follow a shoreline alignment by way of Au Gres along Saginaw Bay around 1932; the former route through
Twining and Whittemore became an extension of M-65 and the section from Whittemore east to Tawas City was added to M-55 as a part of these changes. In 1932, US 23 was moved closer to the lakeshore between
Spruce and Alpena; the former routing was redesignated
M-171. A few years later in 1936, US 23 replaced M-72 between Oscoda and Harrisville and followed a new roadway north to the Spruce area. The M-171 designation was removed from its original routing and applied to the 1932 routing of US 23 by way of
Mikado and
Lincoln. In the middle of 1937,
US 27 was extended concurrently along US 23 between Cheboygan and Mackinaw City. Around the end of the decade, US 23's routing was moved in another location to follow the lakeshore; this time the highway was rerouted between Alpena and Rogers City. M-65 was extended northwards from Lachine through Posen to terminate over the former US 23 routing. US 23 was moved to its current lakeshore routing between Rogers City and Cheboygan in 1940, and
M-33 was extended westerly from Onaway to Afton and north to Cheboygan over the former US 23 roadway while M-68 was extended eastward through Onaway to Rogers City. In early 1941,
a bridge across the Saginaw River connecting Salzburg and Lafayette avenues in Bay City was added to the route of US 23 in the city; at the same time the former routing was redesignated
Bus. US 23. The highway was also realigned between Hartland and Fenton in 1941. By 1945, the northernmost segment of M-65 in downtown Rogers City was redesignated
Bus. US 23, and M-65 was truncated to its junction with US 23 southeast of town, removing the concurrency that existed since 1940. North of Dundee, a more direct alignment to
Azalia was added to US 23, turning the former routing back to local control in late 1947 or early 1948; at the same time, the last gravel section of the highway was paved near Hammond Bay in northwestern Presque Isle County.
Freeway conversion One of the first pieces of what would later become part of US 23's
freeway route was completed in late 1951 or early 1952, when a two-lane bypass was built around the eastern side of
Milan. Two years later, a similar bypass was built from Bridgeport to M-81 on the east side of Saginaw, with the old route becoming a Bus. US 23 designation. Both bypasses would later be upgraded to four-lane freeways by 1961, with the Saginaw one later incorporated into the route of I-75. When the
Mackinac Bridge opened on November 1, 1957, US 23, US 27 and US 31 were extended along the access roadways to the foot of the bridge. The first future freeway portion of US 23 was built in 1957 from north of Ann Arbor to Whitmore Lake as a divided highway. On June 30, 1958, the first stretch of the "Fenton–Clio Expressway" opened, stretching from Fenton to Birch Run. The freeway connection from Dundee south to Ohio was opened on October 1, 1959. In late 1959, the portion from Flint to Birch Run also gained the I-75 designation. In late 1960 or early 1961, a new I-75/US 10/US 23 freeway was built from the north end of the Saginaw bypass to Kawkawlin, utilizing the Zilwaukee drawbridge (later replaced by the
Zilwaukee Bridge) over the
Saginaw River; when it opened, MSHD extended M-13 along the former route of US 23 from the northside of Saginaw into Bay City to the end of the freeway at Kawkawlin. Another section connected the Whitmore Lake area with Brighton in the same timeframe.
General Motors was bidding in 1961 to construct an
electronic highway. US 23 between Ann Arbor and Toledo was under consideration to be the location of this project; the testing for such a roadway was ultimately done at
Ohio State University instead. By the end of the year, freeway sections opened to bypass Saginaw south and ran south to Birch Run, another connected south from Fenton to Hartland, and a third connected Milan with Dundee. The remaining gaps were eliminated with additional freeway openings in 1962: Brighton to Hartland opened in September, and Milan to Ann Arbor opened in November. The I-75/US 23 freeway north of the Kawkawlin area to Standish opened in 1967, and M-13 was shown on maps following US 23's former route through Linwood and Pinconning after the change. The MSHD requested additional Interstate Highway mileage in 1968 under the
Federal-Aid Highway Act of 1968 including a freeway along US 23 between Standish and Mackinaw City. This extension was rejected by Congress on December 13, 1968; instead, Michigan was allotted additional mileage for an extension of I-69 to Flint. Once the last piece of I-75 was completed along the
M-76 corridor in November 1973, the I-75 designation was extended north of Bay City on US 23. The MSHD first proposed a realignment of US 223 in 1965; this change would reroute that highway to replace M-151 in southern Monroe County, and use the US 23 freeway to connect to Sylvania, Ohio. The rerouting change was made in 1977 when Michigan shifted its segment of US 223 as proposed twelve years prior. Instead of running south through
Ottawa Lake, US 223 continued east to the US 23 freeway and south into Ohio. The original bridge across the Saginaw River at Zilwaukee was built in 1960 as a
bascule bridge to allow shipping traffic to use the river. Opening the drawbridge would back traffic up on I-75/US 10/US 23 for upwards of four hours on holiday weekends. Approved in 1974, construction on the replacement bridge started in October 1979. A major construction accident in August 1982 delayed completion of the new Zilwaukee Bridge; a bridge pier partially collapsed when contractors overloaded a section under construction. The affected deck segment tilted to rest higher on one end and lower on the other. The structure is the largest segmental concrete bridge in the country. While that construction was being done, MDOT truncated US 10 at Bay City in 1986; this removed the concurrency between US 10 and US 23 that existed since 1926. A few years later in 1992, the freeway concept for the northeastern LP was revived again when MDOT initiated plans to study and build a new US 23 freeway from Standish northerly to Tawas City, Oscoda or Alpena. This proposal was brought up due to a high level of
tourist traffic along the current routing since the mid-1960s. The FHWA mandated additional environmental studies for the project in 2000, and MDOT withdrew the proposals two years later. In November 2016, construction work on a $92 million project began on the freeway between Ann Arbor and
Whitmore Lake. This construction includes replacement of bridges and reconstruction of off ramps. A year later, the
flex route system opened, using intelligent traffic management and electronic signs to monitor and redirect traffic. The system can open a temporary travel lane on the inner shoulder during rush hour. The flex route project was nationally recognized by
American Association of State Highway and Transportation Officials (AASHTO) in 2018 for Operations Excellence. A $150 million extension to the interchange with I-96 began in 2023 and be completed in 2026. ==Future==