The Border Legion is a 1916 western novel by Zane Grey

Zane Grey

Zane Grey was an American author best known for his popular adventure novels and stories that presented an idealized image of the Old West. Riders of the Purple Sage was his bestselling book. In addition to the success of his printed works, they later had second lives and continuing influence...

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It tells the story of a cold hearted man named Jack Kells who falls in love with Miss Joan Randle, a girl his legion has taken captive near the Idaho border.
It was made into a movie of the same name

The Border Legion (film)

The Border Legion is the name of two western genre films, both based on the 1916 Zane Grey novel.* The 1924 version was a silent film directed by William K. Howard, starring Antonio Moreno and Helene Chadwick....

 in 1924 and again in 1930.
The movie The Last Round-Up (1934) starring Randolph Scott

Randolph Scott

Randolph Scott was an American film actor whose career spanned from 1928 to 1962. As a leading man for all but the first three years of his cinematic career, Scott appeared in a variety of genres, including social dramas, crime dramas, comedies, musicals , adventure tales, war films, and even a few...

, was also based on the novel.