On the afternoon of October 12, 1940, Mix was driving his 1937 Cord 812 Phaeton near Florence, Arizona, (between Tucson and Phoenix) on Arizona State Route 79. Mix had been visiting Pima County Sheriff Ed Nichols in Tucson, and had stopped at The Oracle Junction Inn, a popular gambling and drinking establishment, where he had called and spoken with his agent, when he came upon construction barriers at a bridge previously washed away by a flash flood. A work crew watched as he was unable to brake in time, and his car swerved twice then rolled into a gully, pinning his body beneath. A large polished aluminum suitcase containing a large sum of money, traveler's checks and jewels, which he had placed on the package shelf behind him flew forward and struck Mix in the back of the head, shattering his skull and breaking his neck. The 60-year-old actor was killed almost instantly. Eyewitnesses said Mix was traveling at 80 mph before the accident. A small stone memorial marks the site of his death on State Route 79, and the nearby gully is named "Tom Mix Wash". The plaque on the marker bears the inscription: "In memory of Tom Mix whose spirit left his body on this spot and whose characterization and portrayals in life served to better fix memories of the old West in the minds of living men."
Following a funeral at the Little Church of the Flowers, Tom Mix was interred in the Forest Lawn Memorial Park Cemetery in Glendale, California. He was 60 years old.