Question: Which American Novelist wrote a novel that was made into a 1959 Western film?

Context paragraphs:
Warlock (1959 film): Warlock is a 1959 western film directed by Edward Dmytryk and starring Richard Widmark, Henry Fonda, Anthony Quinn and Dorothy Malone.  The picture is an adaptation of the novel of the same name by American author Oakley Hall.

Thunder in the Sun: Thunder in the Sun is a 1959 western film directed by Russell Rouse starring Susan Hayward and Jeff Chandler.

Angie Dickinson: Angie Dickinson (born Angeline Brown, September 30, 1931) is an American actress.  She began her career on television, appearing in many anthology series during the 1950s, before landing her breakthrough role in 1956 in "Gun the Man Down" with James Arness and the 1959 Western film "Rio Bravo", for which she received the Golden Globe Award for New Star of the Year.

They Came to Cordura: They Came to Cordura is a 1959 Western film co-written and directed by Robert Rossen, starring Gary Cooper and Rita Hayworth, and featuring Van Heflin, Tab Hunter, Richard Conte, Michael Callan, and Dick York.  It was based on a 1958 novel by Glendon Swarthout.

Cast a Long Shadow: Cast a Long Shadow is a 1959 Western film starring Audie Murphy.  It was made by a company Murphy formed with Walter Mirisch.

Day of the Outlaw: Day of the Outlaw is a 1959 Western film starring Robert Ryan, Burl Ives, and Tina Louise.  It was directed by Andre DeToth; this was DeToth's final Western feature film.

Face of a Fugitive: Face of a Fugitive is a 1959 Western film directed by Paul Wendkos.  It stars Fred MacMurray, Lin McCarthy and Dorothy Green and was based on the short story "Long Gone" by Peter Dawson, the nom de plume of Jonathan H. Glidden (older brother of Luke Short).  Dawson was the author of 120 Western short stories and novelettes as well as 15 book length Western serials.  The working title was "Justice Ends with a Gun".

These Thousand Hills: These Thousand Hills is a 1959 Western film starring Don Murray, Lee Remick, Stuart Whitman, Patricia Owens, Alfred Hayes and Richard Egan, and based on the novel of the same name by A. B. Guthrie Jr. It was directed by Richard Fleischer.

The Legend of Tom Dooley: The Legend of Tom Dooley is a 1959 western film directed by Ted Post.  It stars Michael Landon, Jack Hogan, and Jo Morrow.  It was based on the 90-year-old folk song Tom Dooley, which had been inspired by the real-life case of convicted murderer Tom Dula.  The ballad, as sung by the Kingston Trio, was a big hit in 1958 and is the theme song of the film.  The movie's plot is consistent with the lyrics of the song but otherwise bears little resemblance to the actual murder case.

A. B. Guthrie Jr.: Alfred Bertram Guthrie Jr. (January 13, 1901 – April 26, 1991) was an American novelist, screenwriter, historian, and literary historian who won the Pulitzer Prize for fiction in 1950 for his novel "The Way West".

Supporting paragraphs: These Thousand Hills A. B. Guthrie Jr.
Answer: A. B. Guthrie Jr.