The film is about hobos during the 1930s and is set in Oregon. It is based, in part, on the books The Road by Jack London and From Coast to Coast with Jack London by "A-No.-1" (the pen-name of Leon Ray Livingston). However, both books predate the 1930s by a few decades. Carradine's character, Cigaret, uses the moniker that Jack London used on the road, and like London, is portrayed as a young traveling companion to the older A-No.-1 (played by Marvin), but that is where the similarity between Carradine's character and Jack London ends as Cigaret is portrayed in the film as immature, loud-mouthed, and not bright. The title is a reference 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 because somebody ruling over the North Pole would reign over a wasteland.
Shack (Ernest Borgnine) is a merciless, inhumane, and sadistic bully of a conductor on an Oregon railroad during the Great Depression. He takes it upon himself to ensure that no one would ever ride his freight train for free, and that anyone who has would no longer live. Shack has an arsenal of makeshift weapons: a hammer, a steel rod, and a chain. During the opening credits, he hits a hobo who is riding between two cars on the head, causing the "bo" to fall on the tracks and be cut in two by the train's wheels.
A hobo who is a hero to his peers, A-No.-1 (Lee Marvin) manages to hop the train with the younger, less-experienced Cigaret (Keith Carradine) close behind. To create a distraction, A-No.-1 sets fire to the car in which he and Cigaret are riding. At the next stop, A-No.-1 evades the rail yard workers and escapes to the hobo jungle, but Cigaret is caught. Cigaret brags to the workers (Vic Tayback and others) that he was the one who rode Shack's train and that the other tramp burned to death. Most of the workers believe him, and they dispatch another "bo" to spread the word that Cigaret is the one who finally beat Shack. When this tramp arrives in the hobo jungle, A-No.-1 is there, and he is furious to learn that the young braggart Cigaret is taking credit for his deed. A-No.-1 determines to ride Shack's train all the way to Portland to prove that only he is capable of such a bold act. He has another hobo tag his intention high up on the yard water tower, where everyone can see it. When word of this posting arrives in the train shed, Shack is in the process of strangling Cigaret for daring to claim he has ridden Shack's train. Forgotten in the excitement among the yard workers over whether A-No.-1 will succeed, Cigaret slips out unnoticed. The other hobos agree that the first who can successfully ride Shack's train will have earned the title "Emperor of the North Pole." Railroad workers place bets whether A-No.-1 can do it, spreading the news up and down the line by telephone and telegraph, Shack being widely known and disliked.
The next morning is foggy. One of the hobos picks the lock on a switch so that Shack's train, Number 19, will be sent on a branch line, making it easier for A-No.-1 to board. A-No.-1 unhitches the engine and tender from the freight cars to distract Shack further. Shack yells at A-No.-1 in his hiding place in the woods that this prank might cost 10 lives when the fast mail train comes through in just a few minutes. A-No.-1 dismisses this as merely "a ghost story." Hogger (the engineer) and Coaly (the stoker) desperately get the train going again, and they barely succeed in getting it onto a siding, narrowly avoiding a catastrophic collision with the mail train.
A-No.-1 hides inside a pipe on a flatcar and as the morning advances and the fog burns off, he discovers that Cigaret is hiding in another pipe. Shack stops the train on a high trestle so that he and his dimwitted brakeman Cracker (Charles Tyner) can search for hobos more easily. Realizing that he will soon be discovered, Cigaret climbs down the trestle only to discover that A-No.-1 is already relaxing and smoking a cigar in a junk pile at the bottom of a ravine. They reboard the train beyond the trestle but A-No.-1 loses his grip (Shack has sabotaged some of the hand- and footholds) and falls off. Shack strikes Cigaret on the head with a large hammer, causing him to fall off also.
The two men go back to the junk pile and haul several buckets up the slope where they smear the rails with grease. A passenger train is slowed down sufficiently by this that A-No.-1 and Cigaret are able to jump on the roof of one of the cars from an overhead sluice. The two jump off at the Salem yard and steal a turkey. A policeman (Simon Oakland) chases them to a hobo jungle, but is surrounded and forced to humiliate himself by barking like a dog. A-No.-1, by now deeply annoyed by Cigaret's empty boasts, tells the younger man that if he will only listen and allow himself to learn, he has what it takes to become a true hobo, possibly even Emperor of the North Pole. They then get involved in an immersion baptism service as a means of stealing a change of clothes.
Back in the Salem yard, A-No.-1 has once again tagged on the water tower his intent to ride Train 19 all the way to Portland. Shack tells Hogger to take the train out of the yard at regular speed, thereby allowing the two hobos to board easily; Shack clearly wants to settle the matter once and for all. A-No.-1 and Cigaret climb aboard the undercarriage of one of the freight cars, where Shack once again uses a bouncing steel pin on a rope to injure them. In pain, A-No.-1 uses his foot to throw a lever that releases the pressure in the brake lines, causing the train to stop quickly. Coaly is thrown against the firebox, severely burning his back. Cracker is flung from his perch in the caboose, breaking his neck and dying in the process. Cigaret finds A-No.-1 nursing his injuries near a pond and berates him for lacking the strength and courage to go the distance. The younger man insists that he himself is going to become one of the all-time great hobos.
After this tirade, Cigaret reboards the train, but immediately retreats in fear from the hammer-wielding and very angry Shack. Just as Shack is about to deliver a fatal blow, A-No.-1 appears and begins battling Shack. A desperate struggle involving heavy chains, planks of wood and an axe ensues (Cigaret watches from a safe distance). A-No.-1 ultimately has the bloodied Shack at his mercy, but instead of killing him, throws him off the train. In defiance, Shack yells that A-No.-1 has not seen the last of him. The older man then tosses Cigaret off for bragging about how "they" defeated Shack, telling the kid he could have become a good bum but he's got no class. "You had the juice, kid, but not the heart," he yells as the train heads into the distance.
The film was shot in and around the city of Cottage Grove, Oregon along the right-of-way of the Oregon, Pacific and Eastern Railway (OP&E). Willis Kyle, president of the OP&E in 1972, allowed the film company unlimited access to make the film. Oregon, Pacific and Eastern's rolling stock, including two steam locomotives (one being #19, a type 2-8-2 Mikado), appear in the film. This was the location used by Buster Keaton for his 1927 railroad feature The General. Also featured in the film is the Dorena Reservoir, located about 10 miles east of Cottage Grove, and OP&E's railyard in downtown Cottage Grove.
Filming finished on October 5, 1972.
The film was released in North America on DVD on June 5, 2006, under the title Emperor of the North. The Region 2 version was available under general release in the UK from September 3, 2007, under the same title.
On June 16, 2008, Intrada Records released the only commercial CD version of composer Frank De Vol's soundtrack to the public, 35 years after the film's release. The CD, limited to 1,200 copies, immediately sold out. Featuring several unused score cues, it was learned that Bill Medley of The Righteous Brothers had originally recorded the vocals for the film's score, but was replaced at the last minute for unknown reasons by Marty Robbins.
The theme ballad, "A Man and a Train", written by Frank De Vol with lyrics by Hal David and sung by Marty Robbins, appears on his album All-Time Greatest Hits (Catalog# 77425), and the CD The Best of Marty Robbins released by Curb Records in January 2006, both featuring a second verse not used in the film.