Otter Tail Corporation is an energy company based in Fergus Falls, Minnesota. Its subsidiaries include Otter Tail Power Company, BTD Manufacturing Inc., T.O. Plastics Inc., Northern Pipe Products Inc., and Vinyltech Corporation. As of 2007, Otter Tail Power Company serves at least 423 towns at retail and delivers power to about 14 municipal utilities. The company currently has a workforce of over 750 employees, a generating capacity of 660 megawatts, and owns over 5,000 miles of electrical power transmission lines. The company serves 128,500 customers in North Dakota, Minnesota, and South Dakota. Wikipedia