From a 1972 CTA Route Map. Main changes since then were the extension of the line northwest to O'Hare Airport, the flip flop of the two south side lines, the construction of the Orange Line to Midway Airport, and the separation of the Pink Line from the Congress-O'Hare route. At the time, "A" and "B" operation existed, and stations are noted as such. Also shown is the CTA #40 bus route, which at the time served O'Hare Airport nonstop from the Jefferson Park terminal.