Mayor Pro Tem Bob Stephens will step to post as acting mayor. He will be sworn in at noon Tuesday during a special meeting at the Busch Building. Watch the event online live
Council members say the resignation was a result of personal and business conflicts with being able to do his job.
Watch O'Neal explain his resignation here
"Jim had to be absent from several meetings in the recent past because of business issues," Stephens told KOLR10 in his first interview (above) following the meeting. "I think he felt like, because of that, he had to resign because he could not devote the amount of time that he wanted to be a good mayor."
O'Neal has been mayor since 2009; he was halfway through his second term.
O'Neal says he didn't resign over Monday night's issues, which included amendments to the city's smoking ban. That meeting stretched well through the night.
"He certainly had been a good mayor in the last three years," reflects Stephens. "He's done wonders in terms of opening up the process. And he was instrumental in leading us through the Police and Fire Pension Tax about three years ago that had us in danger of tipping into bankruptcy."
O'Neal is the president and CEO of O&S Trucking, Inc.
"The mayor resigned tonight," tweeted Councilman Tommy Bieker. "He was a great leader!"
Stephens is also running for mayor in 2013.