Knife River Corporation, earlier known as Baldwin Contracting Company, is one of the leading aggregate producers in the United States. The company has more than 10 locations. It maintains a work force of over 5,000 employees. Established in 1917, Knife River Corporation provides various types of building materials, such as blocks, foundations, retaining walls and paver systems. The company offers asphalt, cement and ready-mix concrete. It provides engineering, pumping, emulsion distribution and petroleum recycling services. Knife River Corporation additionally offers airport construction, maintenance and leadership development solutions. The company is a subsidiary of the MDU Resources Group, which provides natural resource products.