Story of how the Coast Guard trained to help win World War II.
Lt. Col. Kirby Yorke is posted on the Texas frontier to defend settlers against depredations of marauding Apaches. Col. Yorke is under considerable stress by a serious shortage of troops of his command. Tension is added when Yorke's son (whom he hasn't seen in fifteen years), Trooper Jeff Yorke, is one of 18 recruits sent to the regiment.
Twenty years earlier Farrell killed his mining partner Andrews. Now Andrews daughter arrives to get her father's trust fund. Farrell having rustled Roy's cattle now takes her money from her Lawyer and lets her overhear false information of their next rustling job. With the posse at the wrong location, his men attack the cattle train and Roy on board find himself greatly outnumbered.
Jerry Johnson inherits a 50,000 acre ranch. Lucky Miller wants to take over the ranch. Roy is trying to get a railroad spur right of way. Lucky has a woman come west to marry Jerry to get control of the ranch. After the wedding, Lucky has the owner killed. Roy’s gun is substituted for the murder weapon, so Roy is put in jail.
Roy Rogers takes on crooked wartime profiteers in the musical western Ridin' Down the Canyon. Posing as solid citizens, the crooks spend their evening hours stealing horses from local ranchers, then selling the steeds to the government at exorbitant prices. The head of the bad guys runs a dude ranch where Rogers and his pals (The Sons of the Pioneers) are employed.
Bad guys plot to trick a newly arrived Eastern girl out of a ranch which belongs to her infant ward. Roy, of course, saves the ranch for the girl. Songs include "I'm Headin's for the Home Corral," "He's a No Good Son of a Gun," "Sandman Lullaby," "Song of the San Joaquin," and "I'm a Cowboy Rockefeller."
Judge Kirby is being blackmailed and forced to let outlaws go free. He was once the partner of Roy's father and when Roy reads in the paper that he is in trouble he heads out to help him. Arriving, Roy quickly realizes he has been mistaken for one of the outlaws and is not wanted in town. However he stays, and now posing as that outlaw, hopes to learn who is causing all the problems.
To get the three needed business men to visit the Stevens mine, Roy stages a ride with the Vacaros and has them as honored guests. Seeing a chance to make a lot of money, gangster Harmon joins the ride and then has his men kidnap the three. Having filmed a fake holdup earlier, he uses the film to convince the Sheriff that Roy and the boys were the Kidnapers.
To bring water to their valley, ranchers have raised money to build a dam. When that money is stolen, Allison suggests the ranchers sell their stock to a friend of his thereby getting the money needed to complete the dam. Roy has a clue that Allison was involved in the robbery and is out to get control of the valley. So Roy and the boys try to delay the sale of the stock while they look for proof against Allison.
The Kinkaids and the Harpers both run stage lines and are friendly competitors. Appleby is after the stage line and convinces the two owners to build a spur line to the same town. Then he has both projects sabotaged pitting the friends against each other and running them out of money.