The Apostle Islands, near the southern end of Lake Superior, were named by missionaries who followed the French fur traders into this area. It was thought that there were twelve islands in this archipelago (and therefore the missionaries named the group after the twelve apostles), but there are in fact twenty-two islands. Twenty-one of them are now within the boundaries of Apostle Islands National Lakeshore, a part of the National Park Service. The islands are formed of brown sandstone laid down by braided streams about one billion years ago. Sandstone on several of the islands was quarried for about thirty years, beginning in 1869, to furnish brownstone for urban Midwest buildings.