The first air-conditioned cars were introduced in 1964, the last pre-World War II cars were retired in 1973. New lines were built in expressway medians, a technique implemented in Chicago and followed by other cities worldwide. The Congress branch, built in the median of the Eisenhower Expressway, replaced the Garfield Park "L" in 1958. The Dan Ryan branch, built in the median of the Dan Ryan Expressway, opened on September 28, 1969, followed by an extension of the Milwaukee elevated into the Kennedy Expressway in 1970.