It is the pioneer era and a group of settlers are setting out on the famed Oregon Trail for the Pacific Northwest. A startlingly young Wayne is Breck Coleman, an expert hunter and guide. He is mourning the death of his good friend Ben, another trapper who was killed on the trail for his highly valuable haul of wolf pelts. Breck is asked to guide the wagon train, and he declines—until he sees ne'er-do-well Red Flack has gotten hired on as a cattle driver with the train. Breck realizes from evidence that Flack left behind at the murder scene that he is the killer, and resolves to take the job with the wagon train in order to pursue Flack. Meanwhile, he has become infatuated with Ruth Cameron, a young woman who has recently become orphaned and is setting out on the trail with her brother and little sister to make a new life.
One of the first ever features released in the 70mm widescreen format. Became a Box Office Bomb in part due to that fact, as most movie theaters couldn't accommodate widescreen; the failure of The Big Trail helped end the widescreen experiments of the era and Hollywood would use the 4:3 ratio for the next 20 years. Probably should have been the Star-Making Role for John Wayne, but after the film tanked, Wayne spent the rest of the 1930s making cheap Poverty Row B-Movie westerns. He wouldn't break out as a star until 1939 and Stagecoach.
- Aspect Ratio: One of a handful of films after the end of the Silent Film era shot in widescreen. After this film flopped Hollywood abandoned the format and didn't make widescreen movies until the 1950s, when the rise of television led the studios to resort to stuff like widescreen and color in order to get butts in seats.
- As You Know: The steamboat pilot makes sure to refer to Ruth as "the daughter of Col. Cameron" to let the audience know that she was at one point a child of privilege.
- The Blade Always Lands Pointy End In: Breck is an expert at throwing a knife.
- Call-Back: Early in the film Ruth is in a fancy, frilly dress; Breck recommends that she get some plainer pioneer clothes before starting an arduous cross-country voyage. At the end, when they're settled down in Oregon but Breck has been missing for a while, she takes the frilly dress out and gives it a wistful look.
- Cue the Rain: The pioneers are struggling through a muddy river valley when the Funny Foreigner confidently asserts that the weather's getting better; "there will be no more rain." The next scene shows a deluge pouring down on the wagon train.
- Dances and Balls: The ice between Ruth and Breck stars to melt when he dances with her at a pioneer hoedown.
- Double Standard: Abuse, Female on Male: A Running Gag in the film has a young, bumbling Funny Foreigner, with a forbidding mother-in-law who constantly slaps him every time he screws up.
- Flashback: Breck finding his friend Ben's body, at the lip of the Grand Canyon.
- Hollywood Darkness: Breck looks up and says "Lovely night" in a scene where it's so bright that you can see the shadows of leaves on his shoulder.
- Injun Country
- Breck manages to talk the wagon train past a tribe of Cheyenne by promising that the pioneers won't settle in that area.
- Later, in the desert, a different tribe attracts the train. The pioneers perform the iconic "circling the wagons" maneuver and fight them off.
- Meet Cute: Breck embarrasses himself and pisses Ruth off when he kisses her, Breck thinking mistakenly that she's a childhood friend he hasn't seen in years.
- No Honor Among Thieves: Near the end of the movie, Fleck and Lopez have fled from the wagon train and are attempting to make their escape. When Lopez starts to collapse from hypothermia in the snowbound peaks of the Sierras, Fleck takes his pack and leaves him to die.
- Obnoxious In-Laws: The Funny Foreigner has a shrewish mother-in-law who's constantly smacking him and berating him. He bears it cheerfully.
- "Pan Up to the Sky" Ending: Although most of the sky is obscured by tall redwoods. The camera pans up at the end, after Breck and Ruth's Happy Ending embrace.
- Reports of My Death Were Greatly Exaggerated: The bad guys think they shot Breck off his horse during the buffalo hunt. When he walks out from behind a pioneer's wagon, he says "What's the matter, Lopez? Seein' a few ghosts?"
- Rousing Speech: When the settlers want to turn back in the snowy Sierras, Breck gives a rousing speech about how they have to finish a trail that started all the way back in England.
- Scenery Porn: It's in widescreen, and it was shot on location in Santa Fe and elsewhere, which was unusual for the era. The movie really gets a lot of mileage out of the widescreen format, with some expansive shots of the high desert as well as striking sequences like when Breck goes on a buffalo hunt or the wagon train has to cross a river. The Big Trail looks dramatically different than most any other film made in this era.
- Settling the Frontier: The whole plot, with white settlers trundling west.
- Shell Game: Bill Thorpe's Establishing Character Moment comes when he's ripping off a rube on the steamboat with a shell game. He's promptly tossed off the boat by the captain.
- Thirsty Desert: Five hundred miles through the intermountain West proves challenging. Some of the pioneers have to bury their loved ones.