Prairie du Chien is a city in Crawford County, Wisconsin, United States, and its county seat. The population was 5,506 at the 2020 census. Often called Wisconsin's second-oldest city, Prairie du Chien was established as a European settlement by French voyageurs in the late 17th century. Its settlement date of June 17, 1673, makes it the fourth colonial settlement by European settlers in the Midwestern United States, after Green Bay, Wisconsin; Sault Ste. Marie, Michigan; and St. Ignace, Michigan. The city has many sites showing its rich history in the region.