The highway between M-48 and the northern terminus is a part of the larger Lake Huron Circle Tour.

The highway forms part of the north–south Mackinac–Chippewa county line as it approaches the community of Pickford.

Marie east of the southern terminus of BS I-75, and the roadway is renamed Ashmun Street.

[4] M-129 ends south of the Lake Superior State University campus, home of the annual Banished Words List.

[10] The second usage was for a highway in the Keweenaw Peninsula connecting Phoenix with Eagle Harbor.

[14] Previous to this, the highway continued south into downtown Cedarville on Merdian Road.

A small realignment moved the northern terminus to a new intersection with BS I-75 in Sault Ste.