Iron County, originally part of Marquette County, was first surveyed in 1851. At that time, the area was populated almost exclusively by Native Americans from the Menominee and Ojibwe tribes. Although the original 1851 survey of the county noted the presence of iron ore, European settlers began arriving in numbers in 1875, prospecting for iron ore. In 1880, two important ore strikes were made: the first was by John Armstrong, who opened the Crystal Falls Mine along the Paint River, and the second was by Donald C. MacKinnon, who opened the Iron River (or Riverton) Mine along the Iron River. These two mines were the foundation of the two main population centers of the county, and the success of the mines brought more prospectors to the area, with 70 mines eventually producing ore in the county.