 The 1 @.@ <unk> @-@ mile ( 1 @.@ 720 km ) long route connected two interchanges off Interstate 75 ( I @-@ 75 ) on the south side of Mackinaw City with a tourist welcome center . The southern terminus was at a partial interchange with I @-@ 75 ( exit 337 ) just south of Mackinaw City on the boundary between Emmet and Cheboygan counties . This interchange is about two miles ( 3 km ) north of the northern terminus of US Highway 31 ( US 31 ) . M @-@ 108 followed <unk> Street north from I @-@ 75 into the Village of Mackinaw City past the Thunder Falls Water Park and some local <unk> to an intersection with US 23 . North of the US 23 intersection is the Michigan Welcome Center and other tourist amenities on the west side of the street . State maintenance ends at the intersection with the off @-@ ramp from northbound I @-@ 75 exit 338 . 
