A five-mile (8 km) extension of the route via a short subway connection and the Kennedy Expressway median from Logan Square to Jefferson Park opened on February 1, 1970. It was also built by the City of Chicago using federal money. Just before Logan Square, trains diverted off of the old elevated structure and entered the subway under Milwaukee and Kedzie Avenues to a portal just south of Addison Street, then emerged in the median of the Kennedy Expressway to the temporary terminal at Jefferson Park. The increased ridership that resulted from the extension prompted the CTA to build the second phase of the project, and extend the line the rest of the way to O'Hare. In March 1980, construction began on the O'Hare Airport extension, with the first section between Jefferson Park and Rosemont opening on February 27, 1983, and the final section to O'Hare on September 3, 1984.