Harrisville is a city in the U.S. state of Michigan and the county seat of Alcona County. The population was 493 at the 2010 census. The city is surrounded by Harrisville Township, but is administratively autonomous. Located on Lake Huron, it is an official Michigan Department of Natural Resources Harbor of Refuge. The place was first known as "Davison's Mill" after Crosier Davison, who in partnership with Simeon Holden, had purchased land and water power rights here in 1854.