Ontario Highway 31

Since then, it has been known as Stormont, Dundas and Glengarry (SDG) County Road31 and Ottawa Road31. At the time it was decommissioned in 1997 and 1998, Highway31 began at Highway2 in the community of Morrisburg, approximately from the shores of the St. Lawrence River. It travelled northerly, passing over the CN Kingston Subdivision next to Morrisburg Station,
a former Via Rail stop that was closed in 2021. The route crossed Highway 401 at an interchange (Exit750) and proceeded to be surrounded by farmland. It travels through the community of Glen Becker, Williamsburg and The Sixth as it crosses the municipality of South Dundas. The route then enters the municipality of North Dundas at Winchester Springs, near which it crosses several creeks and irrigation drains. It passes through the community of Cass Bridge, providing access to the conservation area of the same name, before encountering the eastern leg of former Highway43. The highway inexplicably ended at the Dundas–Carleton county boundary south of Vernon for the next decade. On July29, 1936, the highway was extended into Ottawa when the Metcalfe Road through Osgoode and Gloucester townships in Carleton County was assumed by the renamed Department of Highways (DHO); it was now long. While the Metcalfe Road was already fully paved by the time Highway31 was established, the portion of the route assumed in 1927 was unpaved in its entirety. Just over of the route, from Morrisburg to Williamsburg, was paved in 1933. This was followed in 1934 with another of paving south from Winchester. The final 7.25 kilometre gap north of Williamsburg was paved in 1936.

As part of a series of budget cuts initiated by premier Mike Harris under his Common Sense Revolution platform in 1995, numerous highways deemed to no longer be of significance to the provincial network were decommissioned and responsibility for the routes transferred to a lower level of government, a process referred to as downloading. Due to its proximity to Highway16, which was in the process of being upgraded to Highway 416, the entirety of Highway31 was downloaded in 1997 and 1998. On April1, 1997, of the route, from Regional Road8 (Mitch Owens Road) to the Ottawa city limits south of Regional Road32 (Hunt Club Road), was transferred to the Regional Municipality of Ottawa–Carleton. On January1, 1998, the remainder of the route was downloaded, including to Ottawa–Carleton and to the United Counties of Stormont, Dundas and Glengarry.