Ontario Highway 10
|Length:||137.3 km (85.3 mi)|
|History:||Established September 1848
Designated February 26, 1920
|South end:||Northern terminus of Highway 410 – Caledon|
| Highway 9 – Orangeville
Highway 89 – Shelburne
|North end:||Highway 21 / Highway 26 – Owen Sound|
|Major cities:||Owen Sound, Brampton|
|Towns:||Markdale, Shelburne, Orangeville, Caledon|
King's Highway 10, commonly referred to as Highway 10 and historically as the Toronto–Sydenham Road or often as Hurontario Street, is a provincially maintained highway in the Canadian province of Ontario. The highway connects the northern end of Highway 410 with the city of Owen Sound on the southern shores of Georgian Bay, passing through the towns of Orangeville and Shelburne as well as several smaller villages along the way.
The highway was established in 1920 as one of the original provincial highways. It was extended south by 1937 to Highway 2 in Port Credit. That same year, it became the site of the first interchange in Canada at The Middle Road. Since the late 1990s, the southern end has been truncated to its current terminus north of the Brampton–Caledon border.
Highway 10 follows a route originally carved through the virgin forests of Upper Canada in 1848. Its route has remained largely unchanged since that time, and the highway still divides many of the towns it serves, with the exception of Orangeville. It acts as the baseline for the Regional Municipality of Peel; perpendicular sidelines are divided into East and West halves in several cases by the highway.
Beginning at its southern end in Caledon, Highway 10 passes to the west of Valleywood, a suburban community on the fringe of the Greater Toronto Area. The highway presses north-west and rises gently over the Niagara Escarpment, a World Biosphere Reserve. Immediately to the west are the Forks of the Credit, a deep glacial ravine and provincial park regarded for its scenery. The highway passes between several large quarries and enters Caledon Village. Continuing, it reaches Orangeville at Highway 9. The highway passes to the east of Orangville on a bypass, avoiding the business district. At the north end of the bypass, the highway curves and proceeds directly north towards the village of Primrose at Highway 89.
Highway 10 turns west, becoming concurrent with Highway 89 for a short distance, into the town of Shelburne. The concurrency ends in the centre of Shelburne, as Highway 10 splits and turns north and then resumes its northwest course, now running diagonally across the concession road grid. From Shelburne to Owen Sound, the road follows the course of the Toronto–Sydenham Road, a colonization road that predates the division of the land in this area. As such, the road follows a meandering path at an angle to the survey grid. It briefly merges with Ontario Highway 6 in Owen Sound before it ends and Highway 6 goes on to Tobermory.
Historically, Highway 10 follows the combination of the 19th-century stagecoach routes known as Hurontario Street and the Toronto–Sydenham Road, which travelled north from Dundas Street (Highway 5) in Cooksville through Brampton, Orangeville and Shelburne to Owen Sound. It was first designated as a provincial highway on February 26, 1920 when the newly formed Department of Highways assumed the road as far south as Lakeshore Road in Port Credit, on the north shore of Lake Ontario. It was later extended when the provincial government assumed the road running south to Highway 2 in Port Credit. At that point, the total length of the highway was 166 km.
The highway formerly turned west onto Highway 9 and ran concurrently with it through downtown Orangeville along Broadway, then turned north to follow First Street. In 1968, a by-pass around Orangeville was completed, bypassing a short section of the Hurontario Street alignment, which is today a dead end providing access to a hotel. 
In 1998, due to the combination of increasing urbanization and the presence of the parallel Highway 410 through most of the corridor, the provincial government repealed the connecting link agreement for the southernmost 31 km of the highway running through Brampton and Mississauga, which was already effectively under the control of their respective municipal governments.
In 2009, Highway 410 was connected to Highway 10 about 500 metres north of Highway 10's southernmost terminus at the border of Brampton. The 500-metre "orphaned" segment is now discontinuous, and while still technically part of the highway, is only linked to the rest of the highway via a connecting road, and is signed only as "Hurontario Street" rather than with both the street name and highway number.
Also in 2009, a major project to widen two-lane sections of the southern portions of the highway was completed, and the highway is now four lanes wide from Highway 410 north to Camilla. From Shelburne north to Owen Sound, it remains two-lane highway with several "passing lanes" in hillier regions.
|Peel||Caledon||0.0||0.0||Highway 410 south||Highway 10 begins where Highway 410 ends|
|5.2||3.2||Regional Road 9 (King Street) – Bolton|
|14.5||9.0||Forks of the Credit Road|
|18.9||11.7||Regional Road 24 (Charleston Road) – Guelph||Formerly Highway 24|
|Peel–Dufferin boundary||Orangeville||28.3||17.6||Highway 9 east – Newmarket|
|Dufferin||28.9||18.0||Highway 9 west (Broadway) – Arthur|
|Biggles||32.2||20.0||County Road 7 east (Hockley Road) – Loretto
County Road 16 west (5th Sideroad)
|Camilla||38.3||23.8||County Road 8 east (Mono Centre Road) – Mono Centre|
|Primrose||48.6||30.2||Highway 89 east – Alliston||Beginning of Highway 89 concurrency|
|Shelburne||52.6||32.7||County Road 124 north – Collingwood||Formerly Highway 24|
|53.9||33.5||Highway 89 west – Mount Forest||End of Highway 89 concurrency|
|Dufferin–Grey boundary||Dundalk||72.7||45.2||County Road 9 west
County Road 9 east – Creemore
|Grey||Chatsworth||124.5||77.4||Highway 6 south||Beginning of Highway 6 concurrency|
|Owen Sound||137.3||85.3||Highway 21 south / Highway 26 east||End of Highway 6 concurrency; Highway 6 continues west concurrent with Highway 21|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi
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