When the World's Columbian Exposition closed, lack of development along the southern portion of the route led to plummeting passenger numbers. The Chicago and South Side Rapid Transit Railroad Company went into receivership in 1895 and was sold under
foreclosure in September 1896 for $4,100,100. The South Side Elevated Railroad was formed to take over the route in 1897. Service was extended into the newly built
Union Loop in October 1897 connecting the South Side Elevated Railroad with the
Lake Street Elevated Railroad, the
Metropolitan West Side Elevated Railroad, and (after 1900) the
Northwestern Elevated Railroad. These other companies used
third rail electrification to power their trains, so the South Side Elevated Railroad enlisted
Frank Julian Sprague to convert its rolling stock to electrical power. Sprague used his previously untested system of
multiple-unit train control (MU), where multiple self-powered cars could be linked together and controlled by a single person, making the South Side Elevated Railroad the first in the world to use MU operation. ==Branches==