If you see this title and wonder what 'the Pecos' are, don't worry--I had the exact same thought. Apparently, the Pecos river begins in Eastern New Mexico and runs along the Texas border--emptying into the Rio Grande.
Unlike many of John Wayne's early B-movies, this one is not in the public domain and the copy I saw was very crisp and clean. It also appears to have a higher budget than his earlier films for tiny production companies such as Schlessinger. Now it might surprise you to see Wayne in such a film, but through the 1930s, practically all the films he made were B-westerns. It wasn't until after successes in films such as "Stagecoach" and "They Were Expendable" that Wayne graduated to A-pictures and became a top star.
The film begins with a typical baddie deciding that he's entitled to everyone's land. So, when one farmer won't sell out to him, the baddie and his henchmen kill the farmer and his wife--leaving the young boy an orphan. Naturally, the boy grows into a man (John Wayne) intent on exacting justice for his folks. Still, a decade later, the baddie is still forcing people off their land--giving them worthless promissory notes and controlling all the water. Now Wayne is a lawyer and plans on using the law to stop this jerk. Will the law be enough or will Wayne have to resort to his fists and guns? Considering that the baddie controls EVERYTHING, it's not a huge surprise where the film goes next.
The film is nicely polished and watchable. The only negative is that in many of Wayne's early films he had lovable sidekicks--like Gabby Hayes. Here, despite a great villain (Cy Kendall), the supporting cast for the good guys is a bit dull. I missed the usual sidekicks, such as Gabby Hayes, as the deaf guy and his friend were a bit dull. Also, while not exactly a negative, the plot is a bit too familiar--as Wayne and many other western heroes made similar films over the years.
By the way, in a sad note, you see a horse trip and throw its rider near the end (I think this was reused from an earlier film). This is sad, as to get this sort of stunt in the old days, they used trip wires to literally rip the legs out from under the horse--and usually broke the horse's legs in the process!! Fortunately, such things have long ago been outlawed--as it was a terrific waste and morally suspect!