Petoskey is the largest city and the county seat of Emmet County, Michigan, and is the largest settlement within the county. Petoskey h…Petoskey is the largest city and the county seat of Emmet County, Michigan, and is the largest settlement within the county. Petoskey has a population of 5,877 at the 2020 census, up from 5,670 at the 2010 census.