This film was made and originally released as "Emperor of the North Pole." After initial screenings, Twentieth Century Fox executives feared that audiences might think the title indicated a Christmas movie or an Arctic exploration story and so shortened the title to "Emperor of the North," a change that made little sense in terms of audience expectations and none at all in light of the fact that "Emperor of the North Pole" is a hobo term used extensively throughout the film.
The title refers to a joke among hobos during the Great Depression that the world's best hobo was Emperor of the North Pole, a way of poking fun at their own desperate situation since somebody ruling over the North Pole would be ruling over a wasteland.
The main locomotive in the film, OP&E #19, was actually converted to burn oil in the 1920s. For the Emperor of the North, the filmmakers removed the oil bunker in the tender, installed a smaller one in its place, and hid it under the coal pile, so that it appeared to burn coal. This was done so that shoveling coal into the firebox could be used as a tool to add suspense.
The locomotive in the film, #19, still ran on the Yreka Western Railroad for tourist and occasional freight runs until 2008. The line has been severely impacted by the economy, costing it most of its freight and tourist traffic. The future of the line and the locomotive is uncertain, as negotiations continue regarding the future of the rail service.
The film's opening prologue states: "1933 - The height of the Great Depression. Hoboes roamed the land; riding the rails in a desperate search for jobs. Spurned by society, unwanted and homeless, they became a breed apart. Nomads who scorned the law and enforced their own. Dedicated to their destruction was the Railroad Man who stood between them and their only source of survival - The Trains".
Some movie posters for the picture had a long text preamble that read: "This movie is about one hell of a man who lived when Dillinger [John Dillinger] was slamming banks, and Roosevelt [Franklin D. Roosevelt] was awakening the nation. He's a hard-time fast-tracker who's been where it's mean. A grizzly with a sense of humor, an adventurer with holes in his pockets. A wandering rebel, living off the land by his wits and his fists. He goes it alone, he does what he wants - for the beautiful pure sweet hell of it. Who's going to stop him - you? Now he's taking on his biggest run. A challenge no one ever survived. That's why he has to do it!".
Showbusiness trade paper 'Variety' reported that "the production takes its title from hobos crowning 'Lee Marvin' "emperor" for riding Ernest Borgnine's train even a mile, something no other hobo has ever accomplished."