The Interlake Steamship Company, headquartered in Middleburg Heights, Ohio, operates a fleet of nine self-unloading bulk carriers on the Great Lakes. Interlake, a family owned business, is one of the largest U.S.-flag fleets operating on the Great Lakes, and carries approximately 20 million tons of bulk cargo throughout the Great Lakes annually. Those cargoes include iron ore, low-sulfur coal, grain and limestone. The Interlake Steamship Company was founded in 1913, but its roots can be traced back to 1883.