Mich. Comp. Laws § 290.552: Division of state into districts.

Sec. 2.

For the purposes of this act, the state is divided into 7 districts:

(a) District 1 consists of the counties of Arenac, Bay, and Midland plus all counties north of Midland County that are not otherwise designated in a district.

(b) District 2 consists of the counties of Gratiot and Saginaw.

(c) District 3 consists of the county of Tuscola.

(d) District 4 consists of the counties of Genesee, Lapeer, Macomb, St. Clair, and Sanilac.

(e) District 5 consists of the eastern half of the county of Huron using highway 53 as the western boundary.

(f) District 6 consists of the western half of the county of Huron using highway 53 as the eastern boundary.

(g) District 7 consists of the counties of Montcalm, Kent, Isabella, Mecosta, Eaton, Ingham, Clinton, and Shiawassee plus all counties west and south of this district not otherwise designated in a district.