[3] French colonists in the late 17th century were the first Europeans to explore this territory, and they named the St. Joseph River for the patron saint of New France.

After the 1821 Treaty of Chicago was signed, regional tribes of the indigenous peoples ceded much land to the United States, opening the area for American settlement.

The county was set off and organized by the Michigan Territory legislature in 1829; it was named for the river.

This area was settled by members of the three Algonquian-speaking tribes of the Council of Three Fires: the Potawatomi, Odawa, and Chippewa (known as Ojibwa in Canada).

French explorers in a party led by Father Hennepin came upriver from Lake Michigan in 1679.

The county government operates the jail, operates the major local courts, records deeds, mortgages, and vital records, administers public health regulations, and participates with the state in the provision of social services.

The county board of commissioners controls the and has limited authority to make laws or ordinances.

In Michigan, most local government functions – police and fire, building and zoning, tax assessment, street maintenance, etc.