The 25th district was created by the 1850 Michigan Constitution, as the 1835 constitution only permitted a maximum of eight senate districts.

[4] District 25 encompasses all of Huron and Sanilac counties, as well as parts of Macomb, St. Clair, and Tuscola counties.

[5] District 25, as dictated by the 2011 Apportionment Plan, was based in the Thumb, covering all of Huron, St. Clair, and Sanilac Counties and the northern reaches of Macomb County.

Communities in the district include Port Huron, Richmond, Algonac, Marine City, Marysville, St. Clair, Pearl Beach, Sandusky, Bad Axe, Fort Gratiot Township, and Port Huron Township.

[7] Most of the district lied along Lake Huron, and it shared a border with Canada via the St. Clair River.