A voluntary organization that was formed by electric utilities serving customers in eight states and two Canadian provinces to establish operational rules and ensure reliability of the electric grid serving the area. In place for many years, it is now being phased out because of the deregulation of generation and transmission. In its place is a regional transmission organization called the Midwest Independent System Operator (MISO) that will serve a much larger area but will provide the same operational and reliability rules previously provided by MAPP.