It was designated in 1934 and remained relatively unchanged throughout its existence, aside from some minor diversions and a rerouting through Kingston as a result of the construction of Highway 401 in the mid-1950s.

[5][6] Continuing northward, the former route of Highway 38 travels through Hartington, then descends into the Canadian Shield.

North of this point, the scenery drastically changes, with farmland mostly giving way to dense forests and granite rock outcroppings, and the route meanders around rugged terrain and numerous lakes.

It passes through a barren stretch of forest for several kilometres before reaching the community of Parham, where through traffic must turn to remain on the route.

[9] The Department of Highways (DHO) assumed responsibility over the 76.0 km (47.2 mi) Sharbot Lake Road on April 25, 1934,[1] which was gravel-surfaced north of Cataraqui and generally paralleled the K&P Railway.

In 1960 construction began on a full interchange with the western fork as part of a larger project to build the eastbound lanes of Highway 401 to Odessa.

[24] Following World War II, 16.8 km (10.4 mi) of the route from south of Tichbourne to Highway 7 was paved in 1946.

[11][26] 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.

Highway 38 was deemed to serve a local function and was transferred to Frontenac County on January 1, 1998.

[4][29][30] The following table lists the major junctions along Highway 38, as noted by the Ministry of Transportation of Ontario.