The most demanding scene for the actors involved the filming of the human chain employed by the Rangers to cross a treacherous river. The actors themselves had to do the shots without the benefit of stunt doubles. The sequence was begun at Payette Lake in Idaho but had to be completed in the studio tank because the lake was far too dangerous. For Spencer Tracy, who once complained that the physical labors required of actors "wouldn't tax an embryo," it was his most difficult shoot to that point, surpassing even the taxing ocean scenes of his Oscar-winning Capitaines courageux (1937).
The subtitle "Book One -Rogers' Rangers" shows that MGM and King Vidor intended to complete the story in a second film, which was never made due to the lengthy production obstacles that plagued this film. This explains why the characters never make it to the Northwest Passage.
At the beginning of the Revolutionary War, George Washington refused Rogers' request to command troops. Washington suspected that after Rogers' long stay in Britain prior to the outbreak of hostilities that he might be a spy. Washington's fears proved correct, as an infuriated Rogers formed a group called the "Queen's Rangers" (later the "King's Rangers") and fought on the side of the Canadians against the Revolutionary forces. Canada's "Queen York Rangers" claim to be a direct descendant of Rogers' irregular militia.
Members of Rogers' Rangers fought on the American side in the initial battles of the Revolutionary War, Lexington and Concord, in 1775.
According to historical accounts, 204 Rogers' Rangers left for St. Francis and 100 survived to return home.