On October 18, 1942, the Longhorn Army Ammunition Plant, sometimes called the Longhorn Ordnance Works, started producing munitions on a 8,500-acre site near Caddo Lake and Karnack, in Harrison County.
When the US entered World War II, Monsanto Chemical Company began manufacturing explosives on the site and produced roughly 415 million pounds of TNT by 1945. The factory closed later that year but from 1952 to 1956 was managed by the Universal Match Corporation, producing munitions and pyrotechnic devices.
In 1990 the Environmental Protection Agency added the contaminated site to the National Priorities List. The army closed the facility and began a large-scale clean up. Today it is part of the Caddo Lake National Wildlife Refuge and managed by the the U.S. Fish and Wildlife Service.
Information from Texas State Historical Association