According to the Seattle Times, he had been battling dementia and was in hospice.
Knox is the only coach in NFL history to win the Associated Press Coach of the Year award with three different franchises. He won the award in 1973, 1980 and 1984 and finished his career with a 186-147 coaching record, good for a career 56 percent winning percentage.
He is also the only coach in the Seahawks Ring of Honor and has the second-highest winning percentage (behind Pete Carroll) and second most wins in franchise history (behind Mike Holmgren, although Carroll will pass him next season).
Knox was successful out of the gate as a head coach, going 12-2, 10-4, 12-2, 10-3-1 and 10-4 in his first five seasons with the Rams.
Knox was born in the suburbs of Pittsburgh in 1932 and played college football at Juniata College in Huntingdon, Pennsylvania. He served as an assistant coach at Wake Forest and Kentucky, then jumped to the NFL, where he worked as an offensive line coach for the Jets and Lions until he was hired by the Rams in 1973.
From there he would serve as an NFL head coach until 1994, 22 consecutive seasons.
Knox, who was nicknamed "Ground Chuck" because of his preference for attacking via the ground game, was responsible for the first division title in Seahawks history as well as their first playoff win. In his first season with the Seahawks, Knox took the team to the AFC Championship Game.