On the American frontier in 1874, construction of a new railroad forces a necessary rerouting through the town of Rock Ridge, making it prime real estate worth millions. The territorial attorney general Hedley Lamarr devises a nefarious plan to drive the townsfolk away, employing a gang of thugs led by his inept henchman Taggart to eliminate the sheriff and wreak havoc on the town.
In desperation, the townspeople petition Governor William J. Le Petomane to appoint a new sheriff who can protect them. Lamarr manipulates the dim-witted Le Petomane into choosing Bart, a black railroad worker who is about to be executed for assaulting Taggart. He believes that having a black sheriff will cause outrage among the townspeople, plunging Rock Ridge into chaos and leaving it vulnerable to his control.
Initially met with hostility, Bart resorts to taking himself "hostage" to protect against the locals’ outbursts. However, with his sharp intellect and the help of Jim, an alcoholic gunslinger known as the "Waco Kid," Bart begins to disarm the tension. He skillfully subdues Mongo, a massive yet simpleminded henchman, and adeptly navigates an encounter with the opportunistic seductress, Lili Von Shtupp, eventually winning her affection.
Upon Mongo's reluctant release, he informs Bart of Lamarr’s plans concerning the railroad. Bart and Jim make their way to the rail construction site, where they learn from Bart's good friend Charlie that the railroad is indeed intended to pass through Rock Ridge. As they plot against Lamarr, Taggart and his gang aim to obliterate Bart, but Jim's impressive sharpshooting drives them off.
Frustrated with his failed plots, Lamarr rallies a ragtag army composed of criminals, motorcycle outlaws, KKK members, Nazi soldiers, and even Methodists to take down Bart and the townsfolk. However, Bart unites the White townspeople with black, Chinese, and Irish railroad workers, forging a plan that promises mutual aid in exchange for acceptance in the community.
They spend the night crafting a flawless replica of their town to serve as a diversion. Realizing that a mere replica won't suffice, Bart instructs the townsfolk to create copies of themselves as well. To buy time, Bart, Jim, and Mongo construct the "Gov. William J. Le Petomane Thruway," creating a toll booth that successfully delays the raiders.
As the villains attack the decoy town filled with dummies equipped with dynamite traps, chaos ensues when Jim triggers the explosions, launching the bad guys and horses skyward. The townsfolk, joined by the railroad workers, retaliate with fervor, all while Lili provides musical accompaniment amidst the mayhem.
The brawl transcends the confines of Rock Ridge, breaking through the fourth wall and crashing onto a film set where director Buddy Bizarre is filming a Busby Berkeley-style number. The uproar spills over into the studio cafeteria, sparking a food fight that spreads out onto the streets of Burbank.
In an attempt to evade capture, Lamarr hops into a taxi, hiding at Mann's Chinese Theatre where the premiere of Blazing Saddles is taking place. As he settles in, he sights onscreen Bart riding into the theater, blocking his path to escape. Bart confronts him and shoots Lamarr in the groin, then retreats with Jim to relish the movie's finale.
Back in the film, Bart makes it known to the townspeople that his job is complete, and since he’s feeling uninspired, he decides to move on. He meets up with Jim, who is still munching on popcorn, and they set off together to "nowhere special." Their journey takes them briefly into the desert before they dismount, entering a limousine that whisks them away into the sunset.
