The route, which now forms part of Highway 6, was 15.1 kilometres (9.4 mi) long and travelled in a southeast–northwest direction west of Owen Sound.

[8] Unlike previously built roads in the area, the Fort Frances – Kenora Highway, as it was known prior to its opening, was constructed through the rugged terrain of the Canadian Shield.

Rocks, forests, lakes, muskeg, and insects served as major obstacles during construction of the 100-kilometre (62 mi) highway, which progressed from both ends.

Construction on this bridge was underway by March 1936; it was rapidly assembled using Douglas fir from British Columbia as the main structural members.

[9] On July 1, 1936, premier Mitch Hepburn attended a ceremony in front of the Rainy Lake Hotel in Fort Frances.

[9] On a rainy afternoon, at 5:30 p.m., Peter Heenan handed Hepburn a pair of scissors with which to cut the ribbon crossing the road and declare the highway open.

Following the merger, the DHO begin assigning trunk roads throughout northern Ontario as part of the provincial highway network.

[4] On April 22, 1965, the DHO recycled the Highway 70 designation, providing a shorter route for traffic between the Bruce Peninsula and Owen Sound.

[14] It was surveyed in 1854 by Ontario's deputy surveyor, Charles Rankin, to provide a short route between the undeveloped Sydenham (now Owen Sound) and Hepworth townsites.