In the 1990s, a bypass of St. Johns north of Lansing was built, the last freeway segment of US 27 to open under that designation.

I-69/US 27 curved around the east side of Coldwater, connecting to the city's business loop on the south of town.

The freeway intersects the northern end of the business loop immediately east of downtown at an interchange that also features US 12 (Chicago Road).

A third interchange, some three miles (4.8 km) further north, features a distribution center for Walmart stores in the region.

[6][7] In southern Eaton County, the freeway parallels the Battle Creek River north of the junction with M-78.

On the south side of Charlotte, I-69/US 27 turned northward, traversing an area to the east of downtown and crossing the former routing of US 27, which is now part of the business loop for the city.

Further north, the freeway has a junction with M-50, a bridge over the Battle Creek River, and an interchange with the northern end of the business loop next to Fitch H. Beach Airport.

The freeway enters Clinton County, and just north of a crossing of the Grand River, I-69/US 27 turned eastward to separate from I-96.

The freeway continues parallel to the Looking Glass River through suburban areas north of Capital Region International Airport.

The freeway continues due north and intersects M-21 east of town before it turns northwesterly to round the northern side of St. Johns.

Continuing northward as an expressway, the highway has four lanes divided by a median with at-grade intersections at the cross roads.

The expressway transitions back to a full freeway as the trunkline turns north and curves around the east side of Ithaca, meeting the southern end of Ithaca's business loop at Center Road, and the opposite end north of town.

Each city has its own business loop, accessible on the south side through a pair of partial interchanges at Lincoln and State roads.

The freeway crosses the Pine River before intersecting M-46 and the two business loops at another pair of interchanges north of downtown Alma.

The two highways continue in parallel through town before turning to converge north of Mount Pleasant by the airport.

On the east side of that town, the freeway crosses between Little Long and Sutherland lakes before meeting the northern end of the Harrison business loop.

North of that interchange, the freeway parallels the western shore of Houghton Lake and crosses the Muskegon River.

[9] Only one of these followed part of the path of US 27; the Mackinac Trail roughy paralleled the route of US 27 from Grayling north.

[19][20] When a new roadway was built in the St. Louis area in 1930, the former routing into Alma was redesignated US 27A; another US 27A was created in Shepherd around the same time.

[30][31] In the latter half of 1940, US 23 was rerouted to follow the Lake Huron shoreline northwest of Alpena; after this change was completed, US 27's concurrency with US 23 was shortened to start in downtown Cheboygan instead of south of town.

[49] In 1961, the MSHD had proposed that the section of US 27 south of Lansing be built as an electronic highway under a bid through General Motors;[50] the testing for such a roadway was ultimately done at Ohio State University instead.

[52] By the end of the year, the former segment of US 27 between Grayling and Gaylord was turned back to local control, and the section of highway between Indian River and Cheboygan was redesignated M-27.

MDOT rerouted US 27 to follow I-96 around the west side of the city and over the new freeway to reconnect with the exiting routing north of Lansing.

[69][70] Three years later in January 1987, MDOT dropped a proposal to reroute US 27 south of Lansing to the Jackson area, and from there west along M-60 to reconnect with I-69/US 27 at Tekonsha.

[72][73] In 1991, MDOT and the Indiana Department of Transportation petitioned AASHTO to remove the US 27 designation from its concurrency with I-69 in the two states; this request was denied by the association's Special Committee on U.S. Route Numbering at its October 11, 1991, meeting because it would have resulted in a section of US 27 north of Lansing disconnected from the remainder of the highway south of Fort Wayne.

After this opening, US 27 was a full freeway in Michigan from the state line north to St. Johns and from Ithaca to the Grayling area.

[80] The last signalized intersection on US 27 in the state was removed in 2000 when the junction with M-57 was converted to an interchange in southern Gratiot County.

[87] On August 19, 2010, the Michigan House of Representatives passed a resolution recognizing "Old US 27" as a historic road in the state.

[88] According to press reports in 2011, a group advocating on behalf of I-73 is working to revive the freeway project in Michigan.

Since the conversion of the highway into a freeway starting in the 1950s, these business loops served Marshall, Charlotte, Lansing, St. Johns, Ithaca, Alma, St. Louis, Mount Pleasant, Clare and Harrison.