Fort Union may refer to: Fort Union Formation, an economically important geologic formation in the northwestern United States Fort Union National Monument, site of a U. S. Army fort in New Mexico from 1851 to 1891 Fort Union Trading Post National Historic Site, a trading post of the American Fur Company, operating between 1828 and 1867 Fort Union, a major commercial area in Salt Lake County, Utah Fort Union (Wisconsin) See also Fork Union, Virginia