Gladwin is a city in Gladwin County in the U.S. state of Michigan. The population was 3,069 at the 2020 census. Gladwin is the county seat …Gladwin is a city in Gladwin County in the U.S. state of Michigan. The population was 3,069 at the 2020 census. Gladwin is the county seat of Gladwin County. The city is at the southwest corner of Gladwin Township, but the two are administered autonomously.