King's Highway 17, more commonly known as Highway 17, is a provincially maintained highway and the primary route of the Trans-Canada Highway through the Canadian province of Ontario. It begins at the Manitoba boundary, west of Kenora, and the main section ends where Highway 417 begins just west of Arnprior. A small disconnected signed section of the highway still remains within the Ottawa Region between County Road 29 and Grants Side Road. This makes it Ontario's longest highway. The highway once extended even farther to the Quebec boundary in East Hawkesbury with a peak length of about . However, a section of Highway 17 "disappeared" when the Ottawa section of it was upgraded to the freeway Highway 417 in 1971. Highway 17 was not re-routed through Ottawa, nor did it share numbering with Highway 417 to rectify the discontinuity, even though Highway 417 formed a direct link between the western and eastern sections of Highway 17. However, from East Hawkesbury to Ottawa, Highway 17 retained the Trans-Canada Highway routing and signs until it met up again and merged with Highway 417 until 1997 when Highway 17 through Ottawa was downgraded. The Trans-Canada Highway designation now extends along all of Highway 417. Ontario Highway 17 is a very important part of the national highway system in Canada, as it is the sole highway linking the eastern and western regions of the country. Although other small roads connect the province of Ontario with the province of Manitoba, it is the only major highway that links the two, making it a crucial section of Canada's primary commercial and leisure route for all traffic travelling between Canada's largest cities, from Toronto and Montreal in the east to Calgary and Vancouver in the west. History Beginnings With the establishment of the provincial highway network on February 26, 1920, the Department of Public Highways, predecessor to today's Ministry of Transportation of Ontario, sought to establish a network of reliable roads through the southern part of the province. Through July and August 1920, a highway east of Ottawa to Pointe-Fortune at the Quebec boundary, known as the Montreal Road, was assumed by the department. This original routing of Highway 17 followed what is now Montreal Road, St Joseph Boulevard, and the Old Montreal Road eastward out of Ottawa; Laurier Street through Rockland; Regional Road 55 and 26 between Clarence and Plantagenet; Blue Corner Road and Bay Road