Harrison Gypsum Company originally began as a small family operation supplying gypsum to the family farm and neighbors. Originally named the Cement Gypsum Company, Harrison Mine No. 1 was opened near Cement, OK, and underwent the name change to Harrison Gypsum Company in 1956. Over the years the company developed the mining business by supplying raw gypsum rock to nearby manufacturers of Portland cement. As the market area for Harrison Gypsum expanded, gypsum reserves and production capacity also expanded. With business growing, capital investments were made to upgrade to modern mining equipment and improve infrastructure. In 1994, Harrison Gypsum’s mine #2 was named the largest single gypsum mine in the United States by the U.S. Department of the Interior Publication. Today, the total gypsum reserves of Harrison Gypsum Company is estimated to be in excess of a quarter of a billion tons. Although the sophistication of the family operation has grown over the years, the set of principles that established Harrison Gypsum as a trusted name in the industry are still in practice today.We take pride in offering flexible responsive service to our customers, while also maintaining consistent quality standards that produce a premium product. A high standard of service and quality, as well as cost-effective practices in selective mining techniques, led to the establishment of Allied Custom Gypsum Inc. in 1987. Like its parent company, Allied Custom Gypsum caters to a select group of markets. We offer custom products and a series of ground gypsum products, such as flame retardant fillers, animal feed additives, agricultural and turf products, and a high purity food and pharmaceutical grade gypsum. In 2001, Allied Custom Gypsum and Harrison Gypsum merged into a single company, benefiting from the operational synergies and increasing the financial strength present between the two organizations.