Wagon trails Prior to the establishment of Ontario's provincial highway network in 1920, the route that would become Highway 6 was composed of several early wagon trails created during the early settlement of what was then known as
Upper Canada. These trails carved through an otherwise barren wilderness, connecting distant townsites: the
Hamilton–Dover Plank Road between Port Dover and Hamilton, the
Brock Road between Hamilton and Guelph, and the
Garafraxa Road between Guelph and Sydenham (renamed to Owen Sound in 1851) — were opened in the 1830s and 1840s. Further north, the
Southwest Diagonal and the
Centre Road were built through the Bruce Peninsula in the 1840s and 1920s, respectively. In 1837,
Charles Rankin was hired by the
Canada Company to survey a line between Guelph and a new town site on the southern shore of Georgian Bay known as Sydenham. The Canada Company was formed by several British investors to purchase, open, and settle the
Huron Tract, a vast wilderness stretching from Guelph north to Georgian Bay and west to Lake Huron. Rankin's line crossed too many natural obstacles, a result of the tendency to build roads that were straight rather than following the natural topography. Consequently, a new line was surveyed in 1840 by the company's own surveyor, John McDonald, and construction along this new route began. Around the same time, the Van Norman Company constructed a plank road between Port Dover and Hamilton known as both the Hamilton Plank Road and the Dover Road. By 1848, the Garafraxa Road between Guelph and Sydenham was completed. The remaining section between Hamilton and Guelph, known as the Brock Road, was constructed between 1848 and 1850 over the Guelph and Dundas wagon road. The wagon road, merely a trail through the forest, was cleared by the Canada Company in the 1820s to connect the fledgling town of Guelph with the established harbour at Hamilton, thus encouraging settlers to venture inland. Further north, the Southwest Diagonal was surveyed in 1842 by Charles Rankin to provide a short route from the Sydenham townsite to the Hepworth townsite. This route passed through a large swamp and as a result remained an unimproved one lane trail into the 1920s. The Centre Road, the spine of the Bruce Peninsula, was built by the Department of Northern Development in the early 1920s, providing access to communities north of Wiarton. The route followed a telegraph line between Lion's Head and Tobermory and opened up a large area previously accessible only by water. The latter two would not be incorporated into the original route of Highway 6.
Provincial highway When Ontario's Department of Public Highways first established a network of provincial highways on February 26, 1920 to be eligible for federal funding, it included the Hamilton and Dover Plank Road, the Brock Road and the Garafraxa Road. These roads were assumed from the various counties that held jurisdiction over them – Norfolk, Haldimand, Wentworth, Wellington and Grey – throughout June, July and August 1920. Within Wentworth County, the construction of the Clappison Cut through the
Niagara Escarpment was underway by 1921, with the aim of bypassing the winding old route that is known today as Old Guelph Road. The new route, which travelled straight along the boundary between
East and West Flamboro, was assumed on January12, 1921. The province and the City of Hamilton also constructed several new bridges across
Cootes Paradise to create a new northwest entrance into Hamilton. The new entrance, connecting the Toronto–Hamilton Highway (later Highway2) with the incomplete route up the escarpment to Clappison's Corners, was ceremonially opened by the Minister of Public Works and Highways,
Frank Campbell Biggs, on August23, 1922. The Clappison Cut was completed and paved in 1924. ;Clappison Cut construction, 1920–1924 File:Clappison cut 2.png| File:Clappison cut 1.png|A set of rails were installed to remove excavated earth and rock File:Clappison cut 3.png| File:Clappison cut 4.png|Completed work Highway5 and Highway6 travelled concurrently from Highway8 (Main Street) in downtown Hamilton to Clappison's Corners when route numbers were assigned in 1925. Highway5 was long at this time. This situation was short lived however, as Highway5 was redirected west from Clappison's Corners to Peters Corners to meet Highway8 on May25, 1927. Highway6, in turn, assumed the route of Highway5 south to Jarvis. The route was extended further west in 1930, when the newly-renamed Department of Highways (DHO) assumed the road from Highway8 at Peters Corners to Highway24 west of
St. George, as well as the Governor's Road between Highway24 and Highway2 at Paris. The road between Highway8 and Highway24, through
Beverley and
South Dumfries was designated on June18, while the section of the Governor's Road, along the boundary between South Dumfries and
Brantford Township, was designated several months later on September24. These two segments were connected by a
concurrency with Highway24. This brought the length of the route to , including the approximately of Bloor Street and Danforth Avenue between Jane Street and Sibley Avenue, within the Toronto city limits. Below the escarpment, the highway followed what is now the Old Guelph Road, meandering into Hamilton. South of Hamilton, the road to Jarvis was numbered as Highway 5 when route numbers were assigned in the middle of 1925. Highway 5 and Highway 6 travelled concurrently from downtown Hamilton to Clappison's Corners. However, on May 25, 1927, several route numbers were revised, including Highways 5 and 6. Highway 5 was redirected west from Clappison's Corners to Peter's Corners to meet Highway 8. Highway 6, in turn, assumed the route of Highway 5 south to Jarvis. Exactly two weeks prior, on May 11, the Department of Public Highways had assumed the road between Jarvis and Port Dover; this also became a section of Highway 6, establishing its southern terminus for the next seven decades. North of the escarpment to Highway 401, Highway 6 follows the same route that it did in 1920, the Brock Road. North of Highway 401, which didn't exist before the 1950s, the route continued through Guelph along what is now Gordon Street, Norfolk Street and Woolwich Street. This section has since been replaced by the
Hanlon Expressway, built throughout the 1970s. North of Guelph to Owen Sound, the route also follows the same route as it did in 1920, with some small deviations. The section from Fergus north towards Arthur followed the route was of the old Fergus and Arthur Road Company. A "cheap attempt" at paving had been made in the 1920s. The section was straightened, widened and paved with asphalt-based "penetration pavement" in 1930. On April 1, 1937, the Department of Northern Development was absorbed into the Department of Highways, which subsequently took over many development roads as provincial highways. Most of the northern sections of Highway 6 were included amongst these. Highway 68 was designated from Little Current north to Espanola on August 11, 1937. Two weeks later, on August 25, Highway 6 was designated in Bruce County, from Wiarton north to Tobermory. The section within Grey County was designated several months later on November 3. The lone remaining section of what would eventually become today's Highway 6, across Manitoulin Island, was not designated until December 7, 1955. The entirety of Highway 68 eventually became part of Highway 6 in the early to mid- 1980. .
Expressways and bypasses Longwoods Road extension Under the leadership of
Thomas B. McQuesten, who would soon introduce the freeway to Ontario, a new grand entrance to Hamilton was planned. It would cross the Desjardins Canal and terminate at a traffic circle, with Highway 2 continuing east and Highway 6 north. This new road, known as the Longwoods Road Extension, was built partially as a depression-relief project in the early 1930s. Upon completion in 1932, Highway 2 and Highway 6 were routed off the Old Guelph Road onto the new route into Hamilton. This configuration remained until the construction of Highway 403 during the early 1960s, which was built over the Longwoods Road Extension.
Mount Hope Bypass Due to the narrow spacing of buildings in the village of
Mount Hope, a bypass of the village was built in the mid- to late 1950s. The original route is now known as Homestead Drive. The bypass opened on April 26, 1957, at which point the old routing was decommissioned. Construction began between Waterloo Avenue and Stone Road in 1970; this section opened on June 28, 1972. The next section, from Stone Road to Clair Road, opened in October 1973. It and the final section south to Highway 401 were opened on November 7, 1975. Initially, the road featured no interchanges. However, the MTO has long-intended to upgrade the route to a freeway. Construction of the Wellington Avenue interchange began in October 1998; it opened in July 2001. and was fully opened on November 29, 2013, in a public ceremony attended by local officials as well as Guelph
MPP Liz Sandals.
Caledonia Bypass In 1976, a corridor study was completed on Highway 6 between Port Dover and Hamilton, indicating a need for a bypass of Caledonia due to the aging multi-span bridge over the
Grand River, to improve capacity to the developing areas of Nanticoke near Lake Erie, and to reduce the high-volume of truck traffic passing through the town. The bypass was completed in the fall of 1983. The old route through Caledonia is now known as Argyle Street.
Clappison Cut In early 2002, it was announced that the section of Highway 6 north of Hamilton, from Highway 403 north to beyond Highway 5, would be widened to a five lane freeway, with the northbound carriageway featuring an additional truck-climbing lane. This work began in 2006, widening and dividing the highway up the Clappison Cut. The York Road interchange opened on May 23, 2009, following completion of this work. The Plains Road/Northcliffe Avenue intersection was closed the night before and a new section of Plains Road opened on the same day as the interchange. The project to upgrade this segment of Highway 6 was $34 million.
Downloading and changes to route On April 1, 1997, Highway 6 was decommissioned south of Hepworth to Highway 21. The entire length of Highway 70 was subsequently renumbered Highway 6 to rectify the discontinuity. On the same day, the section between the southern terminus at former Highway 24 to the west side of the
Lynn River. These reduced the length of Highway 6 from to . A new segment of Highway 6 was opened to the southwest of John C. Munro Hamilton International Airport in 2004. This building of this route had been planned since the construction of the Caledonia Bypass in 1983. However, concrete plans were not announced until January 1993. However, it had already drawn criticism due to an
old-growth forest located in the path of the route. The planned highway would cost a projected $100 million. However, these plans never came to fruition, and by 1997 a new, shorter route was in the planning stages. Construction of the $33 million route was announced on May 26, 2000 by Transportation Minister
David Turnbull, and began in July 2003. The new route was opened on November 26, 2004. The section through Hamilton at the time followed Upper James Street through the Claremont Access onto the
one-way pairings of Wellington Street and Victoria Avenue then Main Street and King Street. It turned north on Dundurn Street and crossed Cootes Paradise via York Boulevard before turning onto Plains Road and meeting the current route at the now-closed intersection. The responsibility for this routing was subsequently transferred to the City of Hamilton. == Future ==