When three Texas Rangers try to investigate kidnapped Mexicans being used as forced labor in the mines of Silver Bullet, they are framed for murder by the town's corrupt sheriff.
Stephen Westcott and Ed Martin scheme to put Jane Travers' wagon line out of business. They want to use it take over all the wagon- train traffic going west. Hoppy, California and Lucky must make sure that doesn't happen.
When he runs for sheriff, Hoppy is beaten by Jerry Doyle, the gutless wonder voted for by every crook in town. When Hoppy moves to have the new sheriff impeached, outlaw leader Tad Hammond hires forty gunslingers to stop him. Stop Hoppy? Hah!
Hoppy and Lucky have been called in to investigate a series of stage holdups. The robbers are taking gold from Colby's mine and Hoppy suspects it may be ex-outlaw Colby himself. When Speedy strikes gold, Hoppy borrows it and announces a gold shipment hoping to catch the gang and their leader.
Hoppy, Lucky and California search for a mine owned by Trudy Pendleton after it was taken from her by thw swindling gambler Ace Gibson. They find the mine and Hoppy fights Gibson over it.
Sue Morgan gets Hoppy and his friends to join their expedition looking for Indian artifacts. Expedition leader Atwood makes a deal with nearby cattle rustler Morgan to loot the Indian treasures instead and sell them. Hoppy is on to their plan and pretending to leave follows them. Not only is he outnumbered by Morgan's men, but California has himself about to be sacrificed in an Indian ritual.
Before he was killed by Mark Foster's men, Bud Lawton willed part ownership in his ranch to Hoppy and his two pals. When the three arrive they find a fake posing as Lawton. When they expose the imposter, Foster gets the Sheriff to jail them for Lawton's murder.
Joe Weller has instigated a conflict over water rights between two ranchers. The idea is to have the ranchers do each other in then move in and take over. Hoppy and the good guys won't let this happen.
As rustled cattle have mysteriously disappeared, Johnny sends for his friend Hoppy, Hoppy arrives and immediately suspects Dan Slack. Realizing his telegram about Slack was intercepted, he locks up the operator Lafe knowing he can escape. Tailing Lafe he finds a secret entrance to a mine and inside finds the missing cattle. But Slack's men also find him just as the cattle are stampeded through the mine shaft.
Hoppy goes undercover as a gambler from the East when Bar 20 cattle are stolen by unknown rustlers. Brennan/Talbot are twin brothers (one a casino owner, the other a rancher) and Hoppy believes they provide alibis for each other while one is out committing crimes. Hoppy gets a job in the casino to learn more but is exposed when a gambling gunslinger notices him.
U.S. Marshal Hopalong Cassidy is called when a town becomes overun with bad guys. Disguised as a member of a medicine show, Hoppy discovers that the ringleader is none other than sweet li'l ol' Ma Burton.
An evil gang is involved in both cattle rustling and the robbing of stagecoaches. Hoppy must stop them without help from the sheriff who turns out be a major outlaw himself.
A crusading newspaper editor recruits his old friend Hoppy to take the job of Marshall in a town rife with vice and murder directed at helpless miners.
The U.S. Army needs more horses for the Spanish-American War. Hoppy must turn his Bar 20 cowhands into Rough Riders to gather up the horses, and of course bad guys try to sabotage the operation.
Hoppy goes undercover as an outlaw (which permits him, for once, to drink and be mean to children) to track down a bunch of outlaws operating along the border. Loco, the head bad guy, deflects suspicion from himself by pretending to be a moron.
Hopalong Cassidy, boss of the Bar 20 ranch in Texas, rides down the Camino Real in the New Mexico cattle country near Alamogordo, in response to an urgent message from his lifelong sweetheart, Nora Blake, who is in serious trouble. Before he and his saddlemates, "Lucky" Jenkins and "Pappy", can reach her ranch, they are stopped by Clay Allison, a cattle-rustler who is in almost complete control of the district, and wants to extend his holdings by seizing Nora's cattle and driving her out. Seeing Cassidy as a menace to his plans, he has him arrested on a trumped-up charge. Cassidy and his pals shoot their way out of the trouble and reach Nora;s ranch where they learn that Allison's henchmen have murdered her foreman, Tom Dillon, and Allison has sent for a crew of outlaws on the Texas border.
Hoppy clears Lucky on a charge of bank robbery and foils the plot of a crooked lawyer to rustle a herd of pedigree cattle and take over the valley.
Belle Starr has returned from time in prison only to face a hail of bullets, along with rescue by Hoppy and the Bar 20 gang.
Hoppy, Johnny and Windy are fighting a malicious gang trying to stop a cattle drive from reaching a drought-stricken North.
Hopalong Cassidy and Johnny Nelson ride to the mountains to help a man and his daughter save their logging business from someone who is sabotaging their efforts.