[5] Sylvan Valley is locally renowned for "The Golden Mile", a long stretch of sunflowers planted annually alongside the highway by farmer Lynn Orchard since 2013.

[6] Rising out of the valley, Highway 638 enters thick boreal forests as it meanders eastward through an area dotted with small lakes.

East of Leeburn the highway passes several large rock outcroppings before encountering Poplar Dale Road, where it turns south into Ophir.

[7] The Department of Highway (DHO), predecessor to the modern Ministry of Transportation (MTO), assumed the Bruce Mines–Dunn Valley Road on May 9, 1956.

[10][11] The 1.1 km (0.68 mi) portion of Highway 638 through Bruce Mines was transferred from the province to the town on January 1, 1998.

Marie passed a municipal resolution several weeks later which supported the position of Garden River.

[17][18] The safety of the current at-grade intersection at Highway 17 has been called into question by local residents.

[19] The following table lists the major junctions along Highway 638, as noted by the Ministry of Transportation of Ontario.