Oakley Maxwell Hall (1920-2008), born in San Diego, CA, served in the U. S. Marines during WWII. His most famous book, Warlock, was a finalist for the Pulitzer Prize for Fiction in 1958. Other Westerns he wrote are The Adelita (1975), The Badlands (Legends West) (1978), The Children of the Sun (1983), The Coming of the Kid (1985), and Apaches (Legends West) (1986).
It was almost twenty years between his first Western, Warlock, and his second, The Adelita. Hall wrote Adelita and his four other Westerns from 1975 to 1986. He wrote the Ambrose Bierce series of detective novels between 1998 and 2005. His other novels, including mysteries, were published between 1949 and 2007. There were fifteen of those, including Corpus of Joe Bailey, which is the only Oakley Hall book I have read as I try to remember. It is a story of experiences (fictional or otherwise) in WWII and moves to the college years after the war. Hall also wrote under the pen names of "O. M. Hall" and "Jason Manor".
I just watched one of his interviews on YouTube, Story Hour in the Library - Oakley Hall and Michael Chabon. In it, Hall tells how he first got interested in Westerns, which I though was quite funny. His interest came from a stranger who looked like he may be a cowboy near his family's home. The stranger turned out to be Stuart Lake, author of Wyatt Earp - Frontier Marshal.
Warlock was made into a movie starring Henry Fonda, Richard Widmark, and Anthony Quinn. Hall also wrote the novel The Downhill Racers, which was made into a movie starring Robert Redford.
Info from Wikipedia and YouTube.