This short route was extended the following year when the DHO merged with the Department of Northern Development and expanded the King's Highway network north of the Severn River.

By the beginning of World War II, the route reached as far north as Britt; a separate segment connected the town of Burwash with Sudbury.

A commitment to complete four-laning to Sudbury has been made by all three major provincial political parties in Ontario since 1991, but as of 2022 there remains 70 kilometres (43 mi) of two lane highway still to be constructed.

While Highway 6 is located further west, it requires the use of a ferry service between the Bruce Peninsula and Manitoulin Island.

The Canadian Shield dominates the topography, resulting in numerous transverse marshes and rock outcroppings that bisect the highway, with dense forests in between;[7][8] services are limited and distant.

[5][7] Exiting Carling Township, the highway enters The Archipelago, where it scrapes the northeastern edge of the Shawanaga First Nation.

[2] On March 31, 1937, the Department of Northern Development (DND) was merged into the DHO, allowing the latter to extend the provincial highway network north of the Severn River.

[11] Subsequently, through August 1937, Highway 69 was extended 77.75 mi (125.13 km) north to the Naiscoot River, midway between Pointe au Baril and Britt.

[12][13] This extension followed DND trunk routes to Nobel, where a munitions and aircraft factory would soon provide an instrumental role in the war effort.

[12] It was intended to connect these two segments over the next several years; however, the outbreak of World War II in September 1939 halted all non-essential construction due to the short supply of labour and materials.

[15][16] Once the war ended, construction resumed to bridge the 65 kilometres (40 mi) gap between the two sections of Highway 69.

However, that project was shelved by the Progressive Conservative (PC) government of Mike Harris shortly after the 1995 provincial election.

[41][42] The Territorial Reserve did not oppose the construction; however, the land was unobtainable due to a technicality requiring a minimum voter turnout of 65 percent.

[45] Following its completion, Highway 69 was truncated at what is now the south junction of Lake Joseph Road (Exit 189) near MacTier, an overall reduction of over 40 kilometres (24.9 mi) since prior to 1989.

[31] The Liberal government of Dalton McGuinty came to power following the 2003 election with a promise to have a commitment in place within six months.

[47] Construction began on a 20-kilometre (12 mi) segment south of Sudbury to Estaire in January 2005, with route planning studies now completed for the remaining two-lane sections.

[48][49] In June of that year, construction began on a 16-kilometre (9.9 mi) extension of four-laning from Parry Sound to north of Nobel.

[51] The section from south of the Seguin River in Parry Sound to north of Highway 559, bypassing Nobel, opened on October 26, 2010.

[1][58][59] Highway 69 passes through significant tracts of wilderness and forested land, and consequently has seen a rate of animal collisions well above the provincial norm.

Several segments of the four-laned route will include special grade-separated wildlife crossings, the first of which was completed in March 2012.

[65] Although the original plan called for the four-laning of the highway to be complete by 2017, the timeline was pushed back due to delays in environmental assessments and land negotiations with First Nations bands impacted by the construction.

[70] A 19.3-kilometre (12.0 mi) section, from north of the Magnetawan River to Grundy Lake, is funded but has no announced construction timeline.