Port Huron is a city in and the county seat of St. Clair County, Michigan, United States. The population was 28,983 at the 2020 census. The city is bordered on the west by Port Huron Township, but the two are administered autonomously. The city is the largest in The Thumb area of Michigan, and principal community in the Blue Water Area, more recently rebranded as Michigan's Thumb Coast, for tourism purposes.