Post Falls is located four miles (6 km) east of the Washington-Idaho border along Interstate 90 in Kootenai County and is bounded by Coeur dAlene, Idaho to the east, the State of Washington to the west, the Spokane River to the south and the Rathdrum prairie to the north. Post Falls is 20 miles (32 km) east of Spokane, Washington and approximately 100 miles (160 km) south of the Canadian border. Post Falls is a city in Kootenai County, Idaho, United States near the Idaho state line between Spokane, Washington, and Coeur d'Alene, Idaho. The population was 17,247 at the 2000 census, and grew to 27,574 people by the 2010 census, making it Idaho's tenth largest city. Post Falls is named for Frederick Post, a German immigrant who constructed a lumber mill along the Spokane River in 1871 on land he purchased from Andrew Seltice, Chief of the Coeur d'Alene Tribe. The purchase of the land is preserved in a pictograph on a granite cliff in Treaty Rock park.