Montmorency County is a county located in the U.S. state of Michigan. As of the 2020 census, the population was 9,153, making it the second-least populous county in Michigan's Lower Peninsula, behind its southern neighbor, Oscoda County. The county seat is Atlanta.

Oscoda County is a county in the U.S. state of Michigan. As of the 2020 census, the population was 8,219, making it the least populous county in the Lower Peninsula, and the sixth-least populous county in the entire state. The county seat is Mio, an unincorporated community near the center of the county.