The southernmost leg, an 86-kilometre (53 mi) section (including the Bradford–Barrie extension) through Barrie and south to Lake Ontario in Toronto, also known as Yonge Street, was decommissioned as a provincial highway in 1996 and 1997.

[1][2] North of the Severn River, Highway 11 travels through the Canadian Shield; large granite outcroppings are frequent and thick Boreal forest dominates the terrain.

Most of this section is built to freeway standards, although a small number of at-grade intersections remain, primarily between Trout Creek and Callander.

From Cochrane, it passes through communities such as Smooth Rock Falls, Kapuskasing, Hearst and Greenstone, arching across northeastern Ontario westward then south for 613 kilometres (381 mi) before again meeting Highway 17 at Nipigon.

[1][2] Nearly the entire route from Nipigon to Rainy River is a two-lane, undivided road, with the exception of two twinned, four-lane segments approaching Thunder Bay.

Fearing imminent attack by the United States, he sought to create a military route between York (now Toronto) and Lake Simcoe.

[11] In the summer of 1794, William Berczy was the first to take up the offer, leading a group of 64 families north-east of Toronto to found the town of German Mills, in today's Markham.

A north-western extension was branched off the original Yonge Street in Holland Landing and ran into the new settlement of Bradford before turning north towards Barrie.

In 1919, Premier of Ontario Ernest Charles Drury created the Department of Public Highways (DPHO), though much of the responsibility for establishing the route he left to minister of the new cabinet position, Frank Campbell Biggs.

That year saw paving completed between Yonge Boulevard and Thornhill, as well as a bypass of the original route through Holland Landing (now known as York Regional Road 83).

Construction continued for several years to build bypasses of sharp turns, steep grades, awkward rail crossings, and other obstacles.

[45][46] Construction began in 1938 on a road to connect Highway 17 at Nipigon with the gold mines discovered near the town of Geraldton several years earlier.

[51] With the onset of World War II, the need for an east–west connection across Canada became imperative,[52] and construction began on a link between Geraldton and Hearst, a distance of 247 kilometres (153 mi) in 1939.

Due to the shortage of labour, several prison camps were established between the two communities in October of that year and work began to clear a tote road for the movement of supplies over the following winter.

During World War II, large deposits of iron ore were discovered at Steep Rock Lake, around which the town of Atikokan was developed.

[57] The need to connect the burgeoning community to the road network became apparent following a rail strike in August 1950, during which a "mercy train" was delivered to the isolated town.

[58][59][60] The province announced plans for the new highway between Atikokan and Shebandowan the following August,[61] and released the proposed route on October 10; construction began shortly thereafter.

[62][63] The Atikokan Highway was ceremonially opened by premier Leslie Frost on August 13, 1954, although traffic had used the incomplete road beginning in November 1953.

[70] In 1963, Charles MacNaughton, minister of the Department of Highways, announced plans for the Lakehead Expressway to be built on the western edge of the twin cities of Port Arthur and Fort William (which amalgamated in 1970 to form Thunder Bay).

[72] Work began in August 1965, with a contract for a 5 kilometres (3 mi) section of divided highway on the west side of the twin cities.

The largest bottleneck along the highway in the 1940s was between Washago and through Gravenhurst, where construction began in 1947 to realign 23 kilometres (14 mi) between the two towns, including a new high-level bridge over the Trent–Severn Waterway.

A 4-kilometre (2.5 mi) section was opened in September 2001 north of the Huntsville Bypass to south of Novar, mostly along a new alignment alongside the existing highway.

Aubrey Cosens VC Memorial Bridge at the Montreal River in Latchford caused a complete closure and significant detour.

[114] According to the Ministry of Transportation's final report, the failure was caused by a fatigue fracture of three steel hanger rods on the northwest side of the bridge.

[131][132] However, on January 10, 2016, the bridge experienced a significant structural failure in which the deck raised 60 centimetres (2 ft), severing the only highway connection between eastern and western Canada.

[134] The failure caused a significant delay in the construction of the northern span, which did not open until November 23, 2018,[135] The 2.5 kilometres (1.6 mi) of approaches at each end were completed in 2019.

[140][141] Work is ongoing or upcoming to twin or realign the remaining 55 kilometres (34 mi) of two-laned Highway 11/17 between Thunder Bay and Nipigon.

9, crossing the Black Sturgeon River and connecting with the existing four lane route, and; 4.2 kilometres (2.6 mi) through Nipigon, between Stillwater Creek and First Street.

[126][137] Highway 11 between Barrie and Gravenhurst is currently a right-in/right-out (RIRO) expressway (local access permitted, turnarounds via special interchanges), except for a section around Orillia which is a full freeway.

The MTO is currently planning on either converting the existing RIRO expressway to a full six-lane freeway or bypassing it with an entirely new alignment.