Abstract: Papers, 1880-1945, of Chester Hjörtur Thordarson, a Chicago inventor and manufacturer of electrical apparatus, collector of what later became the nucleus of the University of Wisconsin-Madison's rare book collection, and builder on Rock Island, Door County, Wisconsin, of Icelandic-style stone buildings; containing fragmentary documentation of the above activities, some personal papers, correspondence with J. Paul Goode and (in Icelandic) poet Stephan G. Stephansson, and articles by J. Christian Bay. Also included are photographs of the Rock Island buildings, images of Thordarson Electric Manufacturing Company products, and images of Thordarson and his family.