Michigan Compiled Laws, Chapter 600. Revised Judicature Act of 1961 § 600.8101

Sec. 8101. (1) A district court is established in the state. The district court is a court of record. The state is divided into judicial districts of the district court each of which is an administrative unit subject to the superintending control of the supreme court.

(2) When a city is located in more than 1 district, the provisions of section 8251  1 as to where the district court is required to sit shall apply only to that part of such city lying within the particular county or district. A city having a population in excess of 20,000 which is located in more than 1 district is a part of the district containing the greater portion of the population of the city.