In the movie, the crew traveled from the end of steel in Dawson Creek by truck to Fort Nelson, to start work on the highway. But to begin with, the road extended only 50 miles beyond Dawson Creek, to Fort St. John, some 250 miles short of Fort Nelson; so construction of the new road actually began at Fort St. John.
In the movie, the whole Alaska Highway was built by two units, one working south from Alaska, and one working north to meet them. But in reality, there were four groups, each building a different section of the road.
The notice at the end of the credits reads, "The producers are especially grateful to the province of Alberta, Canada for authentic scenes filmed on the Alcan Highway." But the Alcan Highway was not in Alberta at all. Mile Zero is at Dawson Creek, BC, and the highway runs north-west from there, through British Columbia and the Yukon to Alaska.