Ontario Highway 40

Highway 40
Highway 40 highlighted in red
Route information
Maintained by the Ministry of Transportation of Ontario
Length	91.4 km[2] (56.8 mi)
Existed	March 28, 1934[1]–present
Major junctions
South end	Highway 401 in Chatham-Kent
North end	Highway 402 in Sarnia
Location
Country	Canada
Province	Ontario
Highway system
Ontario provincial highways Current Former 400-series
← Highway 37 → Highway 41
Former provincial highways ←  Highway 39

King's Highway 40, commonly referred to as Highway 40, is a provincially maintained highway in the southwestern portion of the Canadian province of Ontario. The 91.4-kilometre (56.8 mi) route links Chatham and Sarnia via Wallaceburg, following close to the St. Clair River. The southern terminus is at Highway 401 south of Chatham, while the northern terminus is at Highway 402 in Sarnia. The portion of Highway 40 between Highway 401 and north of Wallaceburg is within the municipality of Chatham-Kent, while the portion north of there is within Lambton County.

Highway 40 was built as a depression-relief project in 1934. The original routing followed what is now the St. Clair Parkway, but was rerouted to create that scenic road in the mid-1970s. The Sarnia Bypass was opened in 1963 as Highway 40A and renumbered as Highway 40 by 1966; 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 was decommissioned during the Ontario highway transfers in 1998.