History of Secondary Highway 518:
Secondary Highway 518 is a local highway in the District of Parry Sound that provides access from Highway 11 to the Town of Kearney, along with a series of small communities lying between Emsdale and Parry Sound. Highway 518 was designated by an Order-in-Council dated May 9, 1956, and was first depicted on a Preliminary Route Plan prepared by the Department of Highways of Ontario (DHO) in May, 1956. The route of Highway 518 extended east from Highway 69 south of Parry Sound along the Christie Road (Emsdale-Parry Sound Road) for approximately 41 miles (66 km) to the original route of Highway 11 north of Emsdale (today's Highway 592). Shortly thereafter, an eastern extension of Highway 518 was proposed between Highway 11 and Kearney. The eastern extension of Highway 518, which ran from the new Highway 11 Bypass in Emsdale to the western limits of the Town of Kearney, was designated by an Order-in-Council dated December 20, 1956. The eastern extension brought the total length of Highway 518 up to 47 miles (76 km). The route of Highway 518 ran concurrently with Highway 11 for approximately 2 km along the new Emsdale Bypass.
In 1963, Highway 518 was extended northerly from Kearney to Sand Lake. Preliminary Assumption Plans were prepared in March 1963, which showed the proposed extension of Highway 518 along the Perry & Sand Lake Road. The plans were registered on April 1, 1963, and the new highway was designated as Highway 518 by an Order-in-Council, effective May 2, 1963. The section of Highway 518 which passed through the incorporated limits of Kearney was not initially assumed as a Secondary Highway by the DHO. This section of the road remained under municipal jurisdiction for several years, but was ultimately assumed as part of the highway. On March 14, 1969, a Preliminary Assumption Plan was prepared which showed the proposed assumption of approximately 1 mile of the Perry & Sand Lake Road through Kearney. The plan was registered on April 16, 1969, and the new highway was designated as a part of Highway 518 by an Order-in-Council, effective May 8, 1969. The northern extension from Kearney to Sand Lake brought the total length of Highway 518 up to 56 miles (90 km). Jurisdiction over the short bypassed section of Highway 518 which lay sandwiched between Highway 592 (Old Highway 11) and Highway 11 (Emsdale Bypass) was transferred from the province to the Township of Perry, effective April 1, 1971.
The majority of Highway 518 was originally gravel-surfaced, but sections of the highway were paved beginning in the 1950s. The eastern section of Highway 518 from Emsdale to Kearney was paved prior to being designated as a Secondary Highway in 1956. During 1957 and 1958, a primed bituminous surface was laid along the entire western leg of Highway 518 from Highway 69 to Highway 11. The highway was paved with a cold-mix asphalt surface from Sprucedale to the Highway 11 Junction north of Emsdale in 1958 and from Orrville to the Highway 69 Junction in 1963. The northern extension of Highway 518 from Kearney to Sand Lake was paved in 1966. The highway was first shown with a completely paved surface on the 1980-81 Edition of the Ontario Official Road Map.
The route of Highway 518 remained more or less unchanged until the late 1990s, when jurisdiction over the easternmost section of the highway was transferred from the province to the Town of Kearney on January 1, 1998. This 15.1 km section of the highway extended from the western limits of Kearney to Sand Lake. Although the road name "Highway 518" is still commonly used to describe the road between Kearney and Sand Lake, it is no longer a provincial highway beyond the western limits of Kearney.
Another short section of Highway 518 at the highway's western terminus was affected by the completion of Highway 69 New (now Highway 400) south of Parry Sound in 2001. Once the Highway 69 Bypass opened to traffic, the old Highway 69 route (today's Oastler Park Drive) was intended to be transferred to local jurisdiction. This would have meant that Highway 518 would not connect to any other highways west of Highway 69 New. Jurisdiction over the short section of Highway 518 lying between the old and new routes of Highway 69 was transferred from the province to the Township of Seguin, effective December 11, 2002. Today, this section of former Highway 518 is known as Hunter Drive.
Unless posted otherwise, the speed limit on Highway 518 is 80 km/h (50 mph). Services are available in Parry Sound, Orrville, Sprucedale and Kearney.