First designated in 1972, Highway 427 assumed the recently completed 12-lane collector-express freeway of Highway 27, as well as a short freeway north of Highway 401 known as the Airport Expressway. Both routes were upgraded throughout the 1950s and 1960s, eventually becoming intertwined into the present configuration in 1972. The freeway was extended north from Pearson Airport to Highway 7 over the following twenty years. Construction is underway to extend Highway 427 north to York Regional Road 25 (Major MacKenzie Drive); construction began in 2017 and is expected to be completed by 2021.