The first known Europeans to reach Prairie du Chien were French explorers Jacques Marquette and Louis Joliet, who arrived by canoe on June 17, 1673, discovering a route to the Mississippi River. Later travel between Canada and the Mississippi River continued to pass through Prairie du Chien, although routes via the Illinois River were also used. In 1685, the French explorer Nicolas Perrot established a trading post in the area as part of the large and lucrative French fur trade industry. After Americans entered the trade in the nineteenth century, John Jacob Astor built the Astor Fur Warehouse, an important building in the regional fur trade, which was centered in Prairie du Chien. The significance of Prairie du Chien as a center of the fur trade did not diminish until the mid-nineteenth century, when European demand declined, as did game stock.