Highway 63 begins at the Trans-Canada Highway (Highway 11 and Highway 17) in North Bay and travels 63.5 kilometres (39.5 mi) northeast to the Ontario-Quebec provincial boundary, where the highway continues as Route 101 to Témiscaming. Before 1998, the road included a section of Cassells Street extending into downtown North Bay. Prior to this section being removed from the highway, Highway 63's total length was 65.4 kilometres (40.6 mi).
On August 25, 1937, the North Bay – Temiskaming Road was assumed by the Department of Highways as Highway 63. The road existed prior to this point as a northern development road. However, on April 1, 1937, the Department of Northern Development merged into the Department of Highways. As a result, numerous highways were assumed in the northern regions of Ontario in mid-1937. The highway remained unchanged for over 60 years, until January 1, 1998, when the Connecting Link agreement through North Bay from Main Street to Highway 11 / Highway 17 - the North Bay Bypass - was rescinded. As a result, Highway 63 was shortened by 1.9 kilometres (1.2 mi).