Ontario's first roads date back to colonial times, though at that time, much of the important transport was done via the Great Lakes and the major rivers (like the Thames, the Humber, the Ottawa, the French, the Kamistokia, and the Rainy). Early trails connected York to Niagara Falls, York to Windsor, York to Kingston, Kingston to Montreal, York to Georgian Bay (following an Indian portage trail along the Humber). In the 1850s, various Colonization Roads were built into Ontario's wilderness around what is now Algonquin Park, to encourage settlement and resource exploration and extraction. The most famous of such roads is Yonge Street, starting in Toronto, extending up to North Bay and beyond, through mining towns of northern Ontario (eventually becoming today's Highway 11, which continues all the way in an arc, though ThunderBay to Fort Frances. The route is shown incomplete, prior to WWII, in this 1939 map.
While most roads at the time were (or started out as) simple dirt tracks, early road improvement included building notorious "corduroy" roads -parallel rows of cut logs- which often gave bone-rattling, wheel-destroying rides, and made horses fearful of breaking their legs. Later, plank roads were introduced, as split or sawn timber became more readily available by the 1850s. Such roads typically only survived a few seasons without extensive maintenance. Later in the 1800s, macadam roads, surfacing roads with small broken stones from local gravel pits became the preferred medium
Ontario's first provincial legislation governing automobile use came in 1903, including a 15 mile-per-hour (approximately 24 km/h) speed limit. That year, Ontario issued its first 198 licence plates, and in 1909, Ontario issued its first drivers licences (just for chauffeurs). By 1916, Ontario had 50,000 km of gravel roads, and 40,000 km of macadamized dirt roads, for the province's 54,500 registered vehicles.
Over the "Roaring" 1920s, the number of vehicles in Ontario increased from 172,000 to 562,000. Formal road systems were established and organized, resulting in a total of 9,725 miles of county roads and 1,825 miles of provincial highways. The speed limit for highways becomes 25 mph (40 km/h). Road gaps in northern remote areas were filled, like the Cochrane-Hearst Road, and the road between Espanola and Little Current, on the North Shore of Lake Huron.
In 1930, and Ontario engineer experimented with dotted white lines down the centre of a road, and within 3 years they were a standard everywhere. Over the 1930s, roads are extended east from Port Arthur and Fort William (now Thunder Bay) to the Nipigon River Bridge in 1937, a crossing that even today remains the only paved route linking eastern and western Canada. In 1943, to access key wartime mineral resources, a 157-mile stretch between Hearst and Geraldton completes a cross-Canada highway route, connecting to Yonge Street which extends northward form Toronto
In 1939, The QEW becomes the first inter-city divided highway in Canada, running from St Catharines all the way to Toronto. It also features the first cloverleaf interchange in Canada (at Hwy. 10). By the 1940s, preliminary work on what is now Highway 400 (Toronto to Barrie) begins, and construction of some stretches of what will become the 401 were begun between Scarborough an Oshawa.
In 1952, highway numbering series 400 is established to designate freeways, starting with Highways 400 and 401 and 402. By 1958, the country's first freeway, the Queen Elizabeth Way, between Hamilton and Toronto opened up. Plans for a new east-west divided highway from Windsor to the Quebec boundary are announced (Highway 401). Highway 400 from Toronto to Barrie opens. In the north, Atikokan highway (from Fort William) opens for traffic, providing access to mining, lumbering and tourist areas. Highway 69 between the French River and Sudbury opens.
In 1963, the first eight permanent services centres open on Highway 401 (now known as OnRoute) and In 1965, Highway 401 officially named the Macdonald-Cartier Freeway.
In 1974, The ministry lowers speed limits for Ontario highways from 70 to 60 miles per hour (112 to 96 km/h), and from 60 and 55 miles per hour to 50 (96 and 88 km/h to 80 km/h). This was largely an attempt to conserve fuel in the face of international fuel shortages. And in 1977, highways and the Ontario road map start using the metric system.
Here are some history notes, organized by Itinerary Segment (from west to east):