Though one of the first divided highways conceived for Ontario, Highway 403 is one of the most recently completed freeways in the province; the multiple segments of the route did not become continuous until 2002. Planning for the route was underway by 1958, with the completion of the Freeman Bypass along the QEW providing a three-legged junction for the new freeway. Sections of Highway 403 through Hamilton opened between December 1963 and September 1969. An isolated section known as the Brantford Bypass was opened in October 1966, and would remain unconnected to other freeways for over 20 years. Plans for a third segment through Mississauga were contemplated throughout the 1960s, but were not finalized until late 1977, after which construction began. Portions opened at both ends in 1980 and 1981, while the central gap, crossing the Credit River, was completed in December 1982.