History of King's Highway 3A (Windsor):
The second Ontario highway route known as King's Highway 3A connected the Old Detroit-Windsor Ferry Dock & the Detroit-Windsor Tunnel in Downtown Windsor to the Highway 3 Junction at Oliver, located in South Sandwich Township. The Windsor route of Highway 3A was first created out of a route renumbering in 1929. A new provincial highway was assumed by the Department of Public Highways along Huron Church Line Road on July 10, 1929. Highway 3 was relocated from its former route into Windsor via Dougall Avenue onto the newly-assumed route via Huron Church Line Road. The new route for Highway 3 provided a direct connection to the future Ambassador Bridge, which was nearing completion at the time. The old route of Highway 3 from Oliver into Downtown Windsor became Highway 3A (See Map).
Initially, Highway 3A only serviced the Detroit-Windsor Ferry Dock in Downtown Windsor. On November 3, 1930, the Detroit-Windsor Tunnel opened to traffic, and Highway 3A began to serve this new border crossing as well. In 1935, the entire route of Highway 3A from Oliver to Downtown Windsor was renumbered as Highway 3B. The renumbering of Windsor's Highway 3A was apparently done to differentiate this route from an unrelated Highway 3A located in nearby Maidstone. A third (and also unrelated) Highway 3A existed in the Niagara Falls-Welland area between 1927 and 1970.