The Longhorn Army Ammunition Plant, also called the Longhorn Ordnance Works, is a facility for the production of munitions located on a 8,500-acre site beside Caddo Lake at Karnack, Harrison County. In December 1941 the Monsanto Chemical Company selected the site for a facility for the manufacture of TNT, and the company began operation of the $22.5 million plant on October 18, 1942. By August 15, 1945, the plant had turned out 414,805,500 pounds of TNT. The facility closed sometime in November 1945 and remained on standby until February 1, 1952, when it was reopened; it subsequently produced munitions and a variety of pyrotechnic devices under the management of the Universal Match Corporation until 1956. The Thiokol Chemical Corporation, awarded a contract in 1952 for producing solid-fuel rocket motors for the army, built a facility at Longhorn for that purpose between 1953 and 1955. Rocket motors of various kinds were produced at Longhorn until early 1971. The Vietnam War brought an increased demand for pyrotechnic devices, and the Longhorn plant resumed production of such items as flares and ground signals in the 1960s. In 1987 the plant continued to manufacture illuminating devices for the army under the direction of Thiokol, Incorporated, and employed some 962 workers. In 1989 LAAP was one of the sites selected to fire and destroy Pershing IA and II missiles under the terms of the Intermediate Nuclear Forces Treaty between the United States and the Soviet Union, a project completed in 1991.
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Annual Historical Review, Longhorn Army Ammunition Plant, October 1, 1986 to September 30, 1987 (Marshall, Texas: Longhorn Division, Morton Thiokol, Inc., 1987?).
The following, adapted from the Chicago Manual of Style, 15th edition, is the preferred citation for this entry.
“Longhorn Army Ammunition Plant,”
Handbook of Texas Online,
accessed May 27, 2022,
Published by the Texas State Historical Association.
Original Publication Date:
Most Recent Revision Date:
October 10, 2017