The 400-series highways are a network of controlled-access highways throughout the southern portion of the Canadian province of Ontario, forming a special subset of the provincial highway system. They are analogous to the Interstate Highway System in the United States or the Autoroute system of neighbouring Quebec, but under provincial jurisdiction and regulated by the Ministry of Transportation of Ontario (MTO). Although Ontario had been constructing divided highways for two decades prior to their designation, it wasn't until 1952 when these routes were given 400-series designations. Initially only Highways 400, 401 and 402 were numbered; other designations followed in the subsequent decades.