The Milwaukee Road operated long-distance passenger service from Chicago to Milwaukee, the Twin Cities, Omaha, and the Pacific Northwest, and also maintained an extensive commuter service to Chicago's western and northern suburbs. Electro-Motive's streamlined E-units, powered by two separate diesel engines, became the most successful diesel passenger locomotives. The Milwaukee Road's six suburban E9A locomotives were built with added head-end power diesel engines and 350 KW alternators for commuter car lighting, and all six were later used by the North Suburban Mass Transit District and Metra. Milwaukee Road 37A was donated to IRM by Metra and arrived at Union in 1989. It is one of five E-units at IRM, including one E5A, two E9As, one E9B booster unit, and one modified E9AU executive unit.