Knox, who appeared in nearly 40 films mostly in the 1940s, was the mother of television and film actor Mark Harmon, the Los Angeles Times reported Sunday.
The actress began her career in the 1930s as a model, later catching the eye of Hollywood studios. She worked mostly for Universal Studios -- one of her first starring roles was opposite Roy Rogers in 1941's "Sheriff of Tombstone," the newspaper said.
Acting was "a lot of fun but at the time I had two children," she said in the 2009 book "Ladies of the Western."
"I'm just a mother at heart, so I decided it was time to retire from the screen."
Knox made headlines in 1944 when she married Tom Harmon, a Heisman Trophy winner, wearing a wedding dress made from a parachute that saved his life in World War II. Harmon, who was later a television sportscaster, died in 1990 at age 70, the Times reported.
Knox, who died Thursday, is survived by three children: Mark Harmon, and daughters Kristin and Kelly, all of whom pursued acting. Among her nine grandchildren are musicians Matthew and Gunnar Nelson and actress Tracy Nelson. She is also survived by two great-grandchildren.