A rugged, single-minded, self-made, autocratic Texas cattle king, white-haired Tom Dunson owns the sprawling cattle empire with "thousands of heads of good beef." Dunson's greatest challenge, after the Civil War in the year 1865, is that he is in need of cash and there's no cash market for his cattle locally. The beef market for Texan livestock-owners has collapsed in the South due to the war, and its takeover by 'carpetbaggers.'

In a desperate attempt to avoid going broke, he is faced with the arduous task of rounding up the entire herd and transporting it away from the South - north across the Red River on an untested trail-trek to Sedalia, Missouri, where prices were higher and rail facilities stretch out to St. Louis and other markets:

Dunson: And there as they stand, there isn't a head worth a plug three cent piece...It all happened while you were away, Matt. More cattle than a man could gather elsewhere in two lifetimes. And I'm broke. Unless we can move 'em, I'm broke...I'm not gonna take it haunch-backed like the rest around here. There's no market for cattle in Texas...Then I'll take 'em where there is a market, if it means drivin' them a thousand miles.
Matt: Missouri?
Dunson: Yeah.
Matt: That's what I figured.
Dunson: And have you two been doin' a lot of figurin'? While you were at it, did you figure out the best way to get 'em there?
Matt: Which trail to take? Yeah.

His intelligent, gentler foster son, Matthew Garth/Dunson (Montgomery Clift in his first film role, although not released until after his next film, Fred Zinnemann's The Search (1948)) is revealed following a reverse tracking shot. Relaxed and chewing on a blade of grass, he is now grown up and has become Tom's right hand man [symbolically, he wears the snake bracelet that was handed down to him]. Matt suggests a cattle drive route - to San Sabo, then Meridian, and then along the Brazos, but Dunson is immediately critical with two emphatic comments:

That's the long way around...I said, that's the long way.

Matt argues for his suggested route because "there's good water, up, clear all the way up to the Red." Having just returned from the Civil War, he once led a patrol that way and knows the land. Typical of the tension that will develop between father and son, Dunson disagrees about the best way to bring Texas beef (ten thousand head of cattle) north to the rest of the nation. To accentuate their dueling personalities, Groot yells: "Draw!", provoking the two men to wheel around with their guns drawn at each other. Groot teases Dunson that Matt beat him to his gun ("He beat ya").

Speaking alone to Groot, Matt senses the strain and fear in the look of Dunson's face, built up over years of struggle and sacrifice while carving his empire between the time of the wagon train massacre (1851) and the end of the Civil War (1865). Groot is relieved and thankful that Matt has returned safely from the war to join his foster father:

Matt: He's afraid.
Groot: Afraid? Why you're crazy, you're looney.
Matt: Am I?
Groot: Sure, sure, I'm scared too. But I've been here, watchin' and seein'...seein' a man fightin', fightin' with his soul and gut to hang onto this place. Fourteen years of it. And it cost him dear too. It cost him a woman. The only woman he ever wanted...You knew about that. It cost him the killin' of them seven graves, men who tried to take the place away from him. But that weren't hard. Not that.
Matt: No, he knows that kind of fighting. What else?
Groot: And then come the war when you was away. He learned a lot of things for hisself. He learned that a ranch ain't only beef but it's money. But the war took all the money out of the South. He didn't know about money, Matt. He never had none. He didn't know what to do.
Matt: You mean he just doesn't know who to fight.
Groot: Yeah.
Matt: That's all right.
Groot: He's just been waitin' for you to head the herd north and drive. A full drive that's never been done before. Nine, ten thousand head of cattle clear to Missouri.
Matt: We could make it.
Groot: We...well Matt, I'm glad you come home, cause, well, I'm glad you come home.

Dunson orders the rounding up of all the cattle on the range to brand them before pushing north on the old trail to Missouri. His cowhands brand cattle that are already marked with brands from other ranchers - neighboring Meeker and past enemy Diego, but Matt respects the ownership of the steers and lets cowhand Teeler (Paul Fix) free them. Dunson rides up and arrogantly demands unquestioning allegiance from Matt - and is obliged:

Dunson: I said 'Brand him.'
Matt: He's wearing a Meeker iron.
Dunson: I can't see it.
Matt: (To Teeler) Brand him.
Teeler: All right, but the next one up's another Diego.
Matt: Brand him. Put the iron on all of 'em, Teeler. Anything you see, slap it with a 'Red River D' and burn it deep.
Dunson: Why not?
Matt: You're gonna wind up branding every rump in the state of Texas except mine.
Dunson: (challenging him) Hand me that iron, Teeler. (pause) You don't think I'd do it, do ya?
Matt: (smiling) I don't.
Dunson: Matt, I'm goin' to Missouri with every steer, cow, and bull that I can lay my hands on.
Matt: I think Meeker might be real pleased to see our brand on his stock.
Dunson: That I'll argue with Meeker.

Just then, Meeker rides up with other horsemen, knowing of Dunson's drive to Missouri. Word has been spread that there are 'Missouri border gangs' that sabotage cattle drives after crossing the Red River, killing the cowhands and stealing the herds. Dunson is unworried about his own chances: "Nobody's gonna take my cattle." He also forbids one of Meeker's notorious gunmen, Cherry Valance (John Ireland) from checking the herd for Meeker's strays. But then Dunson admits that they have indeed taken some of Meeker's cattle: "All right, we rounded up some of your stock and some of Diego's and some of everybody else's around here...I haven't got the time or the inclination to cut 'em out. So I'll drive 'em to Missouri and give you two dollars a head when I get back." Without any other options, Meeker accepts Dunson's offer.

Cherry changes allegiances and offers to work for Dunson for wages of "ten dollars a month, triple if the steers bring fifteen dollars at the railroad," but there are other risky considerations: "We lose the herd, you lose your wages." After being hired, Cherry admires Matt's gun (and Matt does the same with Cherry's pistol) - a scene often interpreted as homosexually-charged, with Cherry making covert advances toward Matt. Matt and Cherry both prove their well-renowned reputations as sharpshooters to each other in a competitive target practice session with a tin can. Both of them compliment each other on their shooting skills:

Cherry: That's a good looking gun you were about to use back there. Can I see it? (Matt turns, strokes his nose with his thumb and looks a bit amused, then hands his gun over. Cherry takes the gun.) Maybe you'd like to see mine. (Cherry draws his own, and reciprocates by handing it to Matt. Cherry examines Matt's gun.) Nice! Awful nice! (Looking somewhat sideways at Matt) You know, there are only two things more beautiful than a good gun: a Swiss watch or a woman from anywhere. You ever had a good Swiss watch?
Matt: (pointing toward a tin can in the distance) Go ahead! Try it! (Cherry fires a shot and knocks a can into the air. Matt also hits the can in the air with a shot of his own)
Cherry: Hey! That's very good! (Matt shoots at another can, knocking it into the air. Cherry hits it in the air with a shot of his own.)
Matt: Hey! Hey! That's good too! Go on! Keep it going!

Both of them alternate shots to keep a can moving. They both consider themselves expert shots: "That puts two of us at the head of the list." Matt cautions to "leave room for a third" - Dunson, who taught him how to shoot. To Bunk Kenneally (Ivan Perry), Groot observes their "peculiar" kind of fun as a foreshadowing of the future, predicting (unsuccessfully) that the two will fight each other: "They was having some fun - peculiar kind of fun, sizing each other up for the future. Them two's gonna tangle for certain and when they do, it ain't gonna be pretty because they got a thousand miles to do it in."

Groot, who will operate the chuck wagon for the cattle drive, loaded with flour, beans and sugar, halts Bunk's stealing of sugar from the supplies by tossing his knife at him ("I could take the end of your nose off just as easy. A man in your age stealin' sugar!"). Before the big cattle drive, Groot and a Cherokee Indian named Quo (Chief Yowlachie) play a game of poker and Groot is forced to bet a "half interest" in his false "store teeth" to match Quo's silver dollar bet on the table. When Groot loses the bet, it is decided that he can have his teeth back on loan during mealtimes. With the teeth, the Indian dubs himself: "Two Jaw Quo."

A silence falls over all the cowhands when Dunson enters and announces the start of the treacherous cattle drive, uncompromisingly outlining the dangers and ground rules. The main restriction is that once a man signs on, he cannot quit:

Well, we start tomorrow. We're goin' to Missouri with ten thousand head. Most of you men have come back to Texas from the war. You came back to nothing. You find your homes gone, your cattle scattered, and your land stolen by carpetbaggers. Well there's no money and no work because there's no market for beef in the South. But there is in Missouri. So we're goin' to Missouri...Cumberland didn't make it. No one else has. That's the reason I'm here. I want you all to know what you're up against. You probably already know, but I want to make sure you do. We got a thousand miles to go. Ten miles a day'll be good. Fifteen will be luck. It'll be dry country, dry wells when we get to 'em. There'll be wind, rain. There's gonna be Indian Territory - how bad I don't know. When we get to Missouri, there'll be border gangs. It's gonna be a fight all the way. But we'll get there. Nobody has to come along. We'll still have a job for ya when we get back. Now remember this! Every man who signs on for this drive agrees to finish it. There'll be no quittin' along the way, not by me and not by you! There's no hard feelings if you don't want to go. But just let me know now.

Most of the men choose to stay and "sign on" with Matt for the drive that begins at sunup. Groot is the first one to actually sign the oath (with a great flourish of the hand and quill pen), and he confirms his intention to finish the drive with a large X (or cross) signature: "Let me sign first, Matt." His signature clearly denotes that he is illiterate.

In one of the most memorable scenes of the film, the men are just about to embark on their drive early the next morning - it is mostly dark and eerily quiet as dawn on the prairie approaches. On horseback, Dunson surveys the scene, concluding that everything looks ready for their departure. The camera, adopting Dunson's point of view, slowly pans over the entire landscape of mounted cowboys, cattle herd, plains and mountains - a semi-circular 180 degree, counter-clockwise pan as everyone waits for his command to embark on the difficult journey. At the end of the continuous pan, the camera rests on Dunson (taking Matt's point-of-view perspective from his horse), linking the two together!

When everything looks ready, Tom gives his nod to Matt to begin the trek across the Chisholm Trail.

Take 'em to Missouri, Matt.

The drive commences to the railhead (at Sedalia, Missouri) that serves the North and the East. In a montage of images, the cowboys wave their hats in the air, cry and call out "yip-ee" and "ya-hoo" with open mouths to get the cattle moving out on their long trek. A quick close-up of the faces of each one shouting out and whirling around captures their determined enthusiasm and fearlessness. Comically, Groot's own whooping 'yahoo' collapses into a wheezing cough.

Dunson looks out on the sight of the great herd beginning to move:

Dunson: There they are, Matt. Fourteen years of hard work. And they say we can't make the drive.
Matt: They could be wrong.
Dunson: They'd better be.

During their first campfire on their heroic journey, Cherry, who is familiar with the land to the north from a previous trip, suggests a shorter route to a possible cattle market at a railhead in Abilene, Kansas (hearsay from a "girl"), but Dunson stubbornly insists on heading toward Missouri and refuses to alter their direction:

Cherry: Why drive 'em to Missouri? Why not turn west at the Red and head 'em for Kansas?...There's a railroad in Kansas, too...I saw the one in Topeka, and there's one in Abilene...
Buster McGee (Noah Beery): Abilene, that's further west!
Matt: Did you see it in Abilene?
Cherry: I didn't get there. I met a girl in Kansas City. She fancied she could sing. She had...
Matt: You know, if we could head west at the Red...
Groot: We'd save ourselves a heap of...
Dunson (interrupting): We're goin' to Missouri. I've seen buyers and cash in Sedalia. (To Cherry) What have you seen in Abilene?
Cherry: Not a thing. Just the girl told me...
Dunson: We're goin' to Missouri. (Dunson walks off.)
Cherry: (To Matt about Dunson) I suppose if I tangled with him, I'd have to take you on too.
Matt: You'll find him a handful by himself.

The page of the diary turns once again, describing how the rigors of the trip are beginning to take their toll:

To Dunson it was just a job, a big job. Ever north they drove ten thousand cattle crawling through hot, dry country and by the end of the first two weeks they had covered over one hundred and sixty miles. Every mile had taken its toll --- quietly

The sprawling scenes of the long, hard, dusty cattle drive over the trail, driving the cattle herd to market, are realistically detailed - breakfast at 4:30 am, on the trail at 5 am, saddle-sore cowboys, and horse-leg injuries. Even Groot suffers from not having his false teeth - except at mealtimes:

Groot: If you was half-human, you'd give 'em back to me. You can see I could use 'em. Besides, it would help keep the dust out of my mouth.
Quo: Keep mouth shut. Dust not get in.
Groot: Bet I ate ten pounds in the last sixteen days. Before this shenanigan is over, I'll probably eat enough land to incorporate in the Union. The state of Groot.

A second time, Groot lashes Bunk with his bullwhip for stealing more sugar from the chuckwagon:

Your sweet tooth is almost as bad as having a whiskey tongue or liking a woman.

The next diary page describes the tyranny under which they were being driven by Dunson, and the long, laborious, frustrating days, lack of food, water, and rest:

...the days became longer, sleep was at a premium, hard work became harder and Dunson became a tyrant. After three weeks, they reached San Sabo. Here at last was water and a place to rest tired muscles and sore aching bones.

When Matt suggests stopping at San Sabo's watering hole, Dunson disagrees with Matt and demands that they move on to water three or four miles further ahead: "I'll do the thinking. Keep 'em going."

Further along in their dangerous journey, the diary records how difficult the terrain became:

Thirty days on the trail and they reached the Brazos. The way now became harder. Hills and rocks impeded their progress. Each weary mile became endless. The men became morose and worried. The cattle restless and jumpy. Each day the job of...

Coyote howls make the herd jumpy and skittish, but it is Bunk Kenneally who inadvertently sends the herd into an out-of-control stampede when he again selfishly reaches to steal a dab of sugar in the chuckwagon - the third time - and upsets all the pots and pans. It is a furious scene (almost ten thousand cattle running wild) as Dunson cries out: "Stampede!" The wranglers eventually outrun the herd and surround it, but one of the drovers Dan Latimer (Harry Carey, Jr.) is killed. Just a few moments before the deadly stampede, Dan had told Dunson that he was excited about finishing the drive and having one hundred dollars in his pocket for the first time so he can afford to "buy the old Chapman place" and purchase a pair of red shoes for his wife. [The fact that the shoes are colored red is significant, given the other motifs of red in the film, i.e., the Red River, spilt red blood from death, etc.]

A shamed, contrite, and penitent Kenneally feels tremendous guilt for his action. As he stands in front of the chuckwagon where he was reaching for a taste of sugar, his guilt and ostracism are visualized by the judgmental shadows of the returning men passing over him. Latimer, the fallen cowboy is to be buried and grieved over in the morning, and Dunson is faithful to Dan's wishes - his widow is to be paid in full for the drive "as if he finished it," including the receipt of a pair of red shoes:

Dunson: And get her, well, anything else you can think of.
Matt: Like a pair of red shoes, maybe?
Dunson: That's the way he wanted it, wasn't it?

At Latimer's burial in the second funeral scene in the film, the cowhand receives Dunson's eulogy: "You brought nothing into this world and it's certain we can carry nothing out. The Lord gave and the Lord hath taken away. Blessed be the name of the Lord. Amen." Miraculously, a cloud passes over the sun and casts a large dark shadow on the mountainous backdrop during the burial ceremony. [The blackish shadow symbolizes Dunson's violent tendencies that will emerge following the trampling death of a cowboy by his own herd.]

Immediately after the short service, Dunson reaches for a bullwhip and threatens Kenneally with it in a severe public whipping in front of everyone, for the loss of several hundred head of cattle and another man's life: "You started all this...we're three or four hundred head short and you killed Dan Latimer...stealin' sugar like a kid. Well, they whip kids to teach 'em better." Although Kenneally admits he was wrong ("I was wrong, awful wrong") when cattle and supplies were lost in the stampede, he resists being lashed to a wagon wheel and mercilessly punished for his childish crime. He reaches for his gun to defend himself. For the first time in the film, Matt decides to step in and decisively challenge Dunson's authority. Matt beats Dunson to the draw and wounds Kenneally in the shoulder rather than killing him:

Matt: You'd have shot him right between the eyes.
Dunson: Just as sure as you're standin' there. Well, you shot him. You can take care of him.

In an oft-repeated motif and refrain in the film, Groot, Tom's faithful old friend, tells him that he stepped out of line when punishing Kenneally: "You was wrong, Mr. Dunson." The other cowpokes gather around a painfully-wounded Bunk on the ground and administer aid to him - taking the side of the repentant man who felt responsible for what he did and was punishing himself enough. Kenneally is to be treated and then sent back to Texas. Although Cherry admires Matt's fast gun, he accuses Matt of being "too soft":

But your heart's soft. Too soft. It may get you hurt some day.

The next narration in the pages of the diary tells of more hardships, as the cattle drive pushes on toward Missouri with one less grub wagon and short rations:

Forty days and the dust turned to rain. Short rations with Dunson driving both cattle and men. There was no turning back despite the loss of the other grub wagon. Nights were spent in keeping the herd...

Torrential rains soak the cowhands and the soil, turning everything into mud. As they are served short rations at the chuckwagon, the men grumble about the bad food - only beans and "lousy muck" called coffee: "A man can't eat this kind of food. After we lost another grub wagon, we should have turned back." Dunson inflexibly shows no mercy toward Teeler's complaints:

Well, we didn't turn back and we're not goin' to. And even if we had, I couldn't replace what we lost. I'm broke. Got nothin' to buy it with. So you're on short rations and bad coffee. And you're gonna be until we finish the drive. And you're gonna finish it...Like it or not, that's it.

More narration from the next page of the diary tells of the growing rebellion and mutinous feelings among the men toward Dunson - now feeling like an outsider:

Sixty days, tired cattle and tired men. Trouble was not far off. The men sat in small groups, sullen and morose. The food became worse and Dunson was constantly on the alert for the first sign of mutiny. He felt as a man alone...