Jed confronts the Marstons: Corrina (Anne Bancroft, above) and the Colonel (Robert Preston, trapped below).
Mature gives his all in a boisterous, swaggering performance -- at least it's a lot more than he often gave in movies. Jed symbolizes the eventual civilization of the Last Frontier as he gradually learns loyalty to things larger than himself and disciplines himself accordingly. He's not unlike the typical conflicted Mann protagonist, but without Stewart's cool grimness; Mature's a wild man by comparison and the best thing in the movie.
In the end, however, The Last Frontier is a strange synthesis of Fort Apache and, of all things, Gunga Din. Imagine a Gunga Din remake in which the title character not only survives but wins, and you have the finish of Mann's movie. A lone figure is about to ride into an ambush that'll preface a general slaughter of unsuspecting troops. The uncivilized Jed can save the day (and his friend) and alert the troops by firing his rifle. In the end he saves neither Gus nor Marston, but instead of a dead honorary corporal, Jed ends up a live sergeant. Mann usually opts for the redemptive happy ending in his westerns, but this time it seems too neat and too convenient for the hero. The film is simply too romantic to rank among Mann's best work or the great westerns of the decade, but even an inferior Mann western has a lot going for it. Between Mann and Mature, this one has enough to justify a look.