There are currently eight business routes of Interstate 94 (I-94) in the US state of Michigan. These business routes connect I-94 to the downtown business districts of neighboring cities. Seven of the eight routes are business loops which bear the Business Loop I-94 (BL I-94) designation while one is a business spur that bears the Business Spur I-94 (BS I-94). These loops are former routings of I-94's two predecessors in Michigan: US Highway 12 (US 12) or US 25. The westernmost BL I-94 runs through the twin cities of Benton Harbor and St. Joseph along the former routing of US 12 and US 31/US 33 that now includes a section of the Lake Michigan Circle Tour in the state. The loops in Kalamazoo, Battle Creek, Marshall, Albion, and Jackson were also formerly segments of US 12 which were later designated as separate version of Business US Highway 12 (Bus. US 12) through their respective cities before becoming BL I-94s in 1960. The BL I-94 in Kalamazoo was converted into BS I-94 in 2019. The route of the business loop through Ann Arbor was previously US 12 and then later M-14 before receiving its current moniker. The BL I-94 through Port Huron was previously US 25 and then Business US Highway 25 (Bus. US 25).
Benton Harbor–St. Joseph
Business Loop Interstate 94 (BL I-94) is a state trunkline highway and business loop that runs from I-94 through the downtowns of Benton Harbor and St. Joseph. The highway begins at exit 23 on I-94 in Lincoln Township where it runs along Lakeshore Drive, passing through the community of Shoreham. This section of the loop has five lanes (two in each direction with a center turn lane) before it drops a lane in each direction south of Shoreham, and it is part of the Lake Michigan Circle Tour (LMCT). BL I-94 briefly runs concurrently with M-63 along Main Street in downtown St. Joseph. This section widens to a four-lane divided street. BL I-94 separates from M-63 on the one-way pairing of Ship Street (eastbound) and Port Street (westbound) for three blocks before crossing the St. Joseph River to Benton Harbor; the LMCT concurrency ends at this point.
From there, it follows the five-lane Main Street through downtown Benton Harbor through roundabouts at Riverview Drive and 5th Street. At the latter roundabout, the roadway narrows back to three lanes. The easternmost leg of the loop, from Urbandale Avenue easterly to the roundabout at Crystal Avenue, is a three-lane highway and, from there to the eastern terminus at exit 33 on I-94 in Benton Township, is two lanes.
The highway through the downtowns of Benton Harbor and St. Joseph was a part of US 12 when the United States Numbered Highway System was created in late 1926. US 31 was also routed concurrently through the area. The US 33 designation was later added to US 31 from the state line northward to US 12 in St. Joseph in 1937. On November 2, 1960, the I-94/US 12 freeway opened around the Benton Harbor–St. Joseph area, and the former route of US 12 through downtown was renumbered BL I-94. By the next year, US 33 was extended along BL I-94/US 31, and the eastern end of BL I-94 was converted to a divided highway. In 1962, US 31 was rerouted out of downtown Benton Harbor and St. Joseph to follow a new freeway east of Benton Harbor, removing it from BL I-94/US 33. When the business route was first constructed, it had half of a bridgeless diamond interchange each at Crystal and Euclid avenues, with the intent of building overpasses for both crossroads at a later date. Due to a high number of accidents at these two roads, construction began in 1966 to remove the two ramps at Euclid Avenue while also moving that road to an overpass and adding two more ramps at Crystal Avenue. Also as first constructed, the interchanges at each end of the route only consisted of two ramps; a third ramp was added to the eastern end before the highway opened, and the interchange at the western end was converted to a full interchange in 1979.
A new pair of bridges over the St. Joseph River and adjacent Morrison Channel opened in part in 1976 and in full in 1977, replacing bridges built in 1909 and 1911, and were named and dedicated the following month. A planned relocation south of St. Joseph, proposed as late as 1979, was never built. US 33 was truncated in 1986, removing it from BL I-94 and replacing it with M-63 the following year when signage was updated. The Great Lakes Circle Tours were approved by the Michigan Department of Transportation (MDOT) and its counterparts in Minnesota, Ontario, and Wisconsin. In 2016, the section of the business loop concurrent with M-63 was dedicated as part of the West Michigan Pike Pure Michigan Byway.