 Originally, Douglas trains were operated by the Metropolitan West Side Elevated directly into the Loop by means of the Metropolitan's main line.Construction of the Congress Street Superhighway (known now as the Eisenhower Expressway, I-290) in the 1950s required the removal of the Metropolitan's main line, resulting in Douglas trains being routed to the Loop via the Paulina Connector and the Lake Street 'L' similar to the current service.Upon completion of the new Congress branch in the median of the expressway, all trains of the Douglas branch were operated via the Milwaukee-Dearborn Subway to the city's Northwest Side and to .