 The Sarnia Bypass was built between 1963 as Highway 40A and renumbered as Highway 40 by 1965; the original route through Sarnia became Highway 40B until it was decommissioned during the early-1990s.The route was extended to Highway 3 in Blenheim during the early 1970s; however this section would be the sole part of Highway 40 decommissioned during the Ontario highway transfers.The route is long.