He was one of four children; he had an older brother, Robert, and two younger sisters, Margaret and Mary.
He worked in a variety of jobs before devoting himself to writing full-time (or at least in tandem with his cattle farm in the Ozarks) in 1973.
Due to poor sales, Thornburg wrote his subsequent novel Knockover with the intent of writing a more traditional crime novel.
The sale did, however, allow Thornburg to buy his own ranch near Jane, Missouri and work on writing full-time.
His 1976 novel Cutter and Bone received rave reviews, with The New York Times calling it "the best novel of its kind for ten years."
Thornburg landed a four-book contract with Little, Brown and published Black Angus, Valhalla, and Dreamland.