Abstract: Peter Arnold Karthaus (1765-1840) immigrated to the United States from Hamburg, Germany in 1796 and established a mercantile business in the West Branch of the Susquehanna River Valley. The collection documents Karthaus' mercantile business, land development in Clearfield County, Pennsylvania, and his partnership with fellow German immigrant, Frederick W. Geissenhainer, a pioneer in using coal to smelt iron.