Longtime St. Clair County Sheriff Mearl Justus turned in his resignation Tuesday afternoon, according to St. Clair County Board Chairman Mark Kern.

"He has done a wonderful service for this area. I was deeply saddened to receive this resignation," Kern said. "We wish him all the best."

Justus could not be reached for comment.

Undersheriff Rick Watson, the former police chief in Cahokia, will serve as the sheriff until the County Board appoints a replacement. That person will remain until a special election.

Justus served eight terms as sheriff, first elected in 1982. He would have been up for re-election in 2014.

Justus became police chief in Cahokia in 1962.

"He's an icon. Sixty years of service to the community," O'Fallon Police Chief John Betten said. "I've been in law enforcement for nearly 29 (years), and he's the only sheriff I have ever known."

Justus, who turned 81 earlier this month, and his wife, Audrey, moved out of their county-provided apartment above the St. Clair County Jail to the St. Paul's Retirement Apartments nearby a few weeks ago, after Justus underwent gall bladder surgery. But he said in a recent interview that, despite his recent surgery, he is recovering, going to work and planning to finish his term.

Betten called Justus a "policeman's policeman" and an innovator. Justus raised revenue by putting advertising on his squad car.

"He put in a career that will never be matched," Betten said.

Justus served as the chairman of the Major Case Squad of Greater St. Louis in 2000 and also served as the squad's chairman of the board.

He served on the Major Case Squad since it was founded in 1965. Justus also served as president of the Illinois Sheriff's Association.

Madison County Sheriff Bob Hertz called Justus a good cop and great colleague.

"He is a true law enforcement legend," Hertz said. "We are as close as two sheriffs from neighboring counties can be. He is always there when you need him. He will be very hard to replace."

Roger Richards, head of the Southern Illinois Law Enforcement Commission, was a young police chief in Fairview Heights in the 1970s when Justus became his mentor.

"We really looked up to him," Richards said. "He is to law enforcement in this region what the bishop is to the Catholic Church."

St. Clair County State's Attorney Brendan Kelly said he was sorry to hear of Justus' resignation. "Sheriff Justus is a hero to many," Kelly said. "He cannot be replaced, only succeeded. God bless him and his wife."

Justus long was an advocate for expanding the St. Clair County Jail, which was built in 1970. He championed expansion of the jail in 1993 and again sought another expansion recently. He posted the number of occupants on a sign outside the jail that was updated every day.

In 1998, the Illinois Department of Corrections issued a report saying the jail was overcrowded and that there was not enough staff.