Subsequently the name was changed to that of Sumter in honor of General Thomas Sumter, Revolutionary war hero, but the engrossing clerk inserted a "p" in the name, which has since remained Sumpter.

The ethnic and racial makeup of the population was 82.1% non-Hispanic white, 12.0% African American, 0.6% Native American, 0.3% Asian, 0.1% from some other race, 2.9% reporting two or more races and 2.6% Hispanic or Latino.

17.6% of all households were made up of individuals, and 4.5% had someone living alone who was 65 years of age or older.

Sumpter Township is divided between four neighboring school districts.

The entire western edge of the township is served by Lincoln Consolidated School District in neighboring Washtenaw County.

The north-central portion of the township is served by Van Buren Public Schools to the north.

The southwestern portion of the township is served by Airport Community Schools to the south in Monroe County, and a small eastern portion of the township is served by Huron School District.