History of King's Highway 21A:
King's Highway 21A was an alternate route to Highway 21 in the Grand Bend and Forest area during the 1930s. Highway 21A ran from the Highway 21 Junction at Port Franks southerly to the Highway 7 & Highway 21 Junction west of Warwick. Highway 21A was very short-lived; it existed for only four years. The history of Highway 21A dates back to 1934, when the Department of Highways of Ontario (DHO) assumed the county road south of Forest as a new King's Highway. A Preliminary Route Plan was prepared dated January 22, 1934, showing the route of the proposed King's Highway through Lambton County. The proposed highway began at the south limits of Forest and ran southerly to the Highway 7 & Highway 21 Junction between Sarnia and Warwick. The DHO assumed the new route as a new King's Highway on April 11, 1934. The DHO designated the new route as King's Highway 21A. Two years later, the route of Highway 21A was extended north from Forest to Port Franks. A Preliminary Route Plan was prepared dated May 18, 1936, showing the proposed extension of King's Highway 21A to Port Franks. The Forest-Port Franks Road was assumed by the DHO on August 19, 1936. The extension of Highway 21A to Port Franks in 1936 brought the total length of the highway up to 32 km. In the late 1930s, a major route renumbering took place in an effort to simplify route numbering in the area. The entire route of Highway 21A was re-designated as Highway 21 in 1938.