Dickinson County is a county in the Upper Peninsula of the U.S. state of Michigan. As of the 2020 census, the population was 25,947. The county seat is Iron Mountain. Dickinson is Michigan's newest county, formed in 1891 from parts of Marquette, Menominee, and Iron counties. It was named for Donald M. Dickinson, who served as U.S. Postmaster General under President Grover Cleveland. Dickinson County is part of the Iron Mountain, MI–WI micropolitan statistical area.