The story opens in the year 1851, with a wagon train heading west from St. Louis to California. Among the travelers is Thomas Dunson (John Wayne), and as the wagons approach north Texas, Dunson is impressed with the land and decides he will leave the wagon train and head south with his two cows and one bull to start a ranch.
The wagon train leader does not want Dunson to leave, needing him and his cows to make a go of it in California. They argue, and Dunson prevails (hes known to be handy with a gun in addition to being pretty big). He and his long time friend, Nadine Groot (Walter Brennan), will head south and strike out on their own. Dunson's girlfriend Fen (Colleen Gray) is with the wagon train and wants to go with him, but he insists it will be too hard for her, that he will send for her later. Before leaving, he gives her a bracelet that belonged to his mother as a token of his love.
Hours later, as Dunson and Groot approach the Red River, they look back and see a lot of black smoke. They realize that the wagon train is being attacked by Indians. They are too far away to be able to help and realize that the Indians are likely to follow and attack them as well, so they wait. A small group of 5-6 Indians do come and attack them. Dunson and Groot fight them off, killing most if not all of them. Dunson kills one Indian in hand-to-hand combat in the Red River. The Indian was wearing the bracelet Dunson had given Fen, thus Dunson knows his she is dead.
The next morning, a dazed boy comes walking up to Dunson and Groot, trailing a cow. The boys name is Matt Garth. Hes about 14 years old and is babbling something about burning and killing. Dunson slaps the boy, who responds by drawing a gun and pointing it at Dunson. The boy seems to have lost his sense of being dazed. Dunson snatches the gun and knocks the boy down, telling him to never pull a gun on him again. Dunson returns the gun and allows Matt to join them on the trip into Texas. Matt tells Dunson to never try and take his gun from him again.
They cross the Red River and travel south through Texas, finally finding a spot near the Rio Grande that Dunson feels is perfect. Dunson proclaims that all the land north of the Rio Grande Dunson now belongs to him. He tells Garth and Groot that he will brand all the cattle in his future herd with a D double bar (the bars representing the banks of the Red River). Matt wants an M added to the brand, but Dunson says he'll have to earn it.
Shortly after they begin branding the few cattle they brought with them, two men working for a man named Don Diego arrive, telling them that they are on Diego's land. Diego lives 400 miles south of the Rio Grande, in Mexico. Dunson tells them that from now on, he owns everything north of the Rio Grande. One of Diego's men declares that just wont do and draws his gun, Dunson outdraws him and kills him. He tells the other man to go back and tell Don Diego what happened.
Fourteen years pass, and Matt is now grown and played by Montgomery Clift. The Civil War has impoverished the South, and although Dunson has the biggest cattle ranch in Texas, he's broke because no one in the South can afford to buy beef. Dunson determines to start the biggest cattle drive in history, with over 9,000 cows, north to Missouri, where people are buying beef. The going will be hard.
Matt is overseeing the branding of the cattle preparatory to the drive and having the men turn loose any cows belonging to a rancher named Meeker (Davison Clark) or to Don Diego. Dunson rides up and orders that all cattle be branded with the D-Double Bar brand. Matt doesnt agree, but tells the men to go ahead and do as Dunson says. About that time, Mr. Meeker rides up with some of his men, including a hired gun, and asks Dunson for permission to look through the herd to cull out any of his cows. Dunson denies permission, telling Meeker that hes branding all cows he has, regardless of any other brands they may already have.
Things get pretty testy and Matt and Mr. Meekers gunfighter, Cherry Valance (John Ireland) exchange words. As hes grown, Matt has become very handy with a gun himself. Dunson relents somewhat, in that he decides to offer Meeker $2/head for any of his cows that make it to Missouri and get sold. Meeker agrees. Cherry then decides hed like to work for Dunson instead and asks to be hired on. Dunson hires him at $10/month, the going rate for a trail hand.
Matt and Cherry are just itching to have a fight (preferably a gunfight), and Tom realizes its probably inevitable, but he forces them to get along for the time being. They do have an initial challenge where they borrow each others guns and alternately shoot at a tin can, impressing each other with their respective skills.
In the bunkhouse, theres a poker game the night before the drive starts. Quo (Chief Yowlachie) is sitting opposite Groot. Groot has a good hand, but when Quo bets one silver dollar, Groot is aghast. Thats 3 days pay. He asks Matt to loan him a dollar. Matt refuses. Anyway, the rule of the game is that only whats on the table at the time can be used to bet with. Quo asks Groot whats in the small bag on the table and Groot tells him it contains his false teeth. Quo says hell accept half interest in the teeth to cover the dollar bet. Quo has a better hand and demands the teeth in payment. Groot wants to know how hes supposed to eat without his teeth and Quo tells him that come grub time, Groot can use the teeth.
Dunson comes into the bunkhouse and tells everyone that its now or never as far as their decisions to go on the drive. He said thered be no hard feelings for anyone wanting to stay behind and promises theyd still have jobs on the ranch after the drive is over. He tells them that theyll be doing good to make 10 miles a day on the 1,000 mile drive. Theyll face bad weather, dust, Indians and border gangs once they get close to Missouri. For all who go, its expected they will finish the drive, whatever happens. Dunson makes everyone going to sign a piece of paper representing their word to stick it out.
The drive starts the next morning, with nearly 10,000 head of cattle. Dunson quietly tells Matt to Take em to Missour! All the cowboys whoop and holler as they start out. A typical day starts with breakfast at 4:30 and on the trail at 5.
Quo holds Groot to the results of their bet, only loaning the teeth back to Groot at mealtimes. Groot is not happy about that. He tells Quo that the teeth help him keep the dust out of his mouth. He complains that before the drive is over, hell probably eat enough land to get himself incorporated in the Union as the State of Groot. Quo still says no. Dunson isnt happy about it either, complaining that Groot mumbles and needs to have his teeth in to be understood.
Dunson drives the men hard. There are stories of several ranchers who have attempted to get to Missouri and been ambushed and murdered. Cherry has heard that the railroad has reached Abilene, Kansas and the going is safer, but Dunson refuses to change his planned route because Cherry hasn't seen a railway in Abilene with his own eyes.
One of the wranglers, Dan Latimer (Harry Carey Jr.), wears checkered pants that stand out. He speaks about using the $100 he will earn on the drive to buy a place to farm/ranch, and a pair of red shoes for his wife. Unfortunately, he wont get the chance to do that, because hes killed in a subsequent stampede, but Dunson tells Matt to make sure the widow gets Dans money and whatever else. Matt replies, like a pair of red shoes?
The group is 30 days (about 160 miles) into the drive with no major issues. One cowboy remarks that he doesnt like that. He likes a balance of good and trouble, not just one or the other. Trouble does come though, when Bunk Kenneally (Ivan Parry) gets into the supply of sugar (he would regularly sneak up and dip his fingers into the sack whenever he could, which got him in trouble with Groot). Everyone has been on their best behavior as far as being quiet, because the cattle are on edge, tired from the month-long drive, with coyotes milling about. Worries were that the cows would stampede if something spooked them. Bunk clumsily knocks over some of the cook pots when hes getting into the sugar and thats enough noise to start a stampede.
When Latimer turns up missing, after the cows had stopped and calmed, a search begins. They find the remains of his checkered pants among a bunch of dead cattle. Dunson reads over his remains the next morning. As he puts the Bible back on the wagon, he sees Groots bullwhip and picks it up, calling out to Bunk. Calling attention to the fact that Bunk started all this, resulting in 400 cows dead and Latimer too, he refers to the action of stealing sugar being like a little kid. He says the solution to that would be a good whipping. He tells Teeler to strap Bunk to a wagon wheel.
Bunk is remorseful about the dead cows and Latimer, but he wont stand to be whipped. He goes for his gun. Hed likely have been shot dead by Dunson, but Matt draws faster and shoots Bunk in the shoulder, saving his life. Dunson turns to Matt and says, you shot him, you take care of him! Matt sends Bunk back home with two horses. Cherry tells Matt that while hes real fast with a gun, hes got a soft heart, and that will get him hurt some day. Matt says that could be, but dont count on it.
40 days out, with reduced rations (after one wagon was destroyed in the stampede) and the men increasingly restless, Dunson reminds them that they all signed on to see it through, like it or not.
A cowboy named Sutter (William Self) rides up, his head bandaged and barely able to talk, with a deep rope burn around his neck. He reports that he was from the Garwood herd (2,000 cows) on the way to Missouri, when they were ambushed by about 100 bandits. He only survived because the rope around his neck frayed. He said he met a scout who told him the railroad was in Abilene, but when Dunson asks Sutter if the scout saw the railroad himself, Sutter can't remember. Dunson again says they're heading for Missouri.
Naylor, Fernandez and another hand tell Dunson theyve had enough (right after theyd watched Dunson set his gunbelt down while he was preparing to go get some water). Dunson tells them they cant leave. Groot tosses a loaded and cocked rifle to Dunson as the three go for their guns, and together with shots fired by Matt and Cherry, they kill the three wranglers. Dunson orders the three buried, announcing that hell read over them in the morning. That prompts one of the cowboys to say: Plantin and readin, plantin and readin. Why, when youve killed a man, why try to read the Lord in as a partner in the job?
Matt argues with Dunson over the need to confront and kill the three men. He and Groot both tell Dunson hes wrong to do such things. Groot patches up a bullet wound on Dunsons lower left leg.
That night, Teeler, Kelsey and Laredo are on watch, but they decide to take some ammunition and flour and ride out, headed back home. The next morning, Dunson sends Cherry and Buster to go get the three and bring them back, dead or alive. He intends to make examples of them and stop anymore men from leaving.
The herd arrives at the Red River. Matt wants to give everyone a rest and cross first thing in the morning. Dunson will have none of that, and orders the crossing to begin immediately. The process continues into the night. Between 30-40 head are lost. Dunson is limping pretty bad on his wounded leg and pulls heavily from a bottle of whiskey he has. Hes exhausted, but refuses to sleep until Cherry gets back with the three cowboys who left, to make sure no one else tries to leave.
After three days, Cherry comes back with Laredo and Teeler. Kelsey had refused to come back so Cherry said he shot him. Dunson announced that he was going to hang Laredo and Teeler. Matt tells him no. Dunson braces himself to stand up and face Matt and Matt shoots him in his gun hand. When Dunson tries to draw his gun, he cant hold onto it and it drops. He then reaches for it with his left hand and Buster shoots the gun away.
Matt announces that hes taking over and will be taking the herd to Abilene. He says that Dunson will be left behind. Groot offers to stay with Dunson, but he tells Groot to go with the others. He then tells Matt that hell come after him and will kill him. Groot later calculates how long before Dunson gets to another town, rounds up some new men, and catches up to them. From then on, the men are all nervous and jumpy, waiting for Dunson to approach them from behind.
One of the steers is discovered dead on the trail, filled with Apache arrows. Matt sends Buster and Cherry ahead with rifles to scout and keep watch. Buster comes riding back, all excited, with news that theres a wagon train about 18 miles ahead, the Donegal Party, headed from New Orleans to Nevada, to set up a saloon for gambling, drinking and partying. There are dancing girls with the wagon train. Matt decides that the men need and deserve some distraction and decides to head the herd to the wagon train before continuing on to Abilene.
As the herd approaches the Donegal wagon train, they hear shooting. The Donegal party is under attack by Apaches. Matt gives orders for all the men to split up in two groups and come at the Indians from the sides, while he and a few others will ride down the middle. It takes some time to get all the men rounded up and ready, so Matt and the few others go ahead and ride straight to the wagons, jumping right into the middle of the circled wagons and helping fight the Indians who were circling around, yelping and shooting their arrows.
Matt finds himself side by side with a very attractive woman who is firing a rifle (but not very well). Shes Tess Millay (Joanne Dru). He tells her to load the rifles and hell shoot. She perceives that hes angry about something and wants to know what. About that time, she takes an arrow to the right shoulder, pinning her to a wagon. Matt cuts the shaft so she is free from the wagon, but he has to finish the Indian fight before helping more. The rest of the men come charging down the hill and the men come out from behind the wagons and the Apaches decide to disperse.
Matt returns to pull the arrow from Tesss shoulder, then he sucks the poison out. She slaps him across the face, then passes out.
Theres a big party in camp that night. Tess asks Groot to tell her all about Matt, because she wants to know. She also wants to talk to Matt before they get back on the trail the next day. Groot goes and finds Matt (hes out in the fog, on watch) and tells Tess where he is. She goes out there and starts talking away. She tells him that he needs to talk to her in return, that talking about his concerns and fears is the way to deal with them. He doesnt need all that much convincing and they quickly get very comfortable with each other.
As its raining hard and there are worries about the level of the next river to be crossed. Matt decides they need to do it right away, even though its nighttime. Meanwhile, Dunson has gathered 8 or so new men and is on the chase. Nine days after the herd has left the wagon train, Dunson and his men come across the wagons. Tess immediately announces that shell take care of Mr. Dunson. She leads him to her tent and considers shooting Dunson with a derringer as he sits in her tent talking to her, but he knows she has the pistol and is prepared to shoot her first if need be. It doesnt come to that, however.
Dunson notices Tess is wearing his mothers bracelet and asks her how she got it away from Matt. At first, she sarcastically says she stole it, then admits she loves Matt and he gave it to her. Tess tells Dunson she wanted to go with Matt on the drive, but he said no, it was too dangerous and tough. That reminded Dunson of the day when he turned down his girl, Fens, request to go with him. Hes nevertheless bound and determined to go find and kill Matt and tells Tess she cant say or do anything to change his mind.
Dunson admits his disappointment in Matt, saying he was the son he never had and that Matt was due to inherit his ranch before all the trouble happened. Dunson suddenly takes a fresh look at Tess and offers her half of everything he owns in exchange for her bearing him a son. She says shell do it, if hell stop pursuing Matt. He says no, so she begs instead to be allowed to go with him after Matt, explaining how it tore her apart when Matt left. Dunson realizes her words echo his dead love Fen's words, and he agrees.
Matts understandably stressed about whether they will even find a railroad in Abilene, and the fact that Dunson is hot on his trail. Fortunately, they hear a train whistle in the distance and come across a train, about 12 miles from Abilene. The engineer is very thrilled to see the herd, as are the townspeople who come riding out to meet and greet them. They tell Matt to drive the herd right down Main Street so all the people can see.
In Abilene, Mr. Melville (Harry Carey Sr.) represents the Greenwood Trading Company of Illinois, and offers immediately to buy the entire herd. Matt has no experience at selling cows, so hes hesitant to accept the $20/head offer. Mr. Melville then tells him to go out and find the best price he can for a lot of 500 cows. Melville said hed match the price and still buy the whole herd. It ends up being $21/head. Matt signs the contract and receives a check, which he told Melville to make out to Thomas Dunson, for $50,000, with the balance to be paid once a final tally is arrived at. Matt makes sure the men all get paid right away.
Matt returns to his room at the Hotel Royale and is shocked to find Tess in there, all dressed in black. She apologizes for appearing as if shes in mourning. She tells him Dunson is camped outside town and will be coming to get him in the morning. They spend the night together.
Next morning, everyone has gathered at the front of the hotel, waiting. Buster rushes in through the cows on his horse to announce that Dunson and 10-12 men were riding in. Dunson tells the men with him to remember where they each stand in all this, which apparently is to hang well back and not interfere. Dunson dismounts on the far side of the railroad tracks and sets out with that very purposeful John Wayne walk, through the cows, and across the tracks.
Cherry, realizing that Matt is not likely to draw and shoot it out with Dunson, confronts Dunson before he gets to Matt. They both draw and shoot, wounding each other. Cherry falls, but Dunson continues on. He tells Matt to draw, but Matt refuses. Dunson draws and empties his gun, shooting all around Matt, knocking his hat off and grazing his right cheek, drawing blood.
He then walks up to Matt and questions what he has to do to make a man of him. He then grabs and tosses away Matts gun, reminding Matt that he once told him never to try that again. Dunson then punches Matt in the face 2-3 times, knocking him down. He drags him back up ready to hit some more, but Matt has finally had enough and shocks Dunson by punching him and knocking him down. They brawl awhile more until Tess fires a pistol into the air, stopping the action. She berates them verbally, then decides maybe they should go ahead and pummel each other and turns away.
Dunson tells Matt to marry that gal. Matt says, "When are you going to stop telling people what to do?" Dunson says, "After just one more thing." He tells Matt that after they get back to Texas, hes going to make the brand the double bar D with an additional name (he scrawls out an M in the dirt), and says to Matt, You earned it!