ABC Supply is the largest wholesale distributor of roofing in the United States and one of the nation//s largest distributors of siding, windows and other select exterior building products. Founded in 1982 and headquartered in Beloit, Wis., the company operates more than 350 branches in 45 states and the District of Columbia. It has distinguished itself by following a single, simple guiding principle - treat contractors with respect and help them succeed by understanding their businesses and offering products and services carefully selected to meet their unique needs.