Every year another local municipality takes up the issue of whether or not to allow residents to keep chickens in their yards. Most end up coming up with an ordinance setting out guidelines, but otherwise agreeing to it. In the Rockford Illinois area officials in the town of Poplar Grove has sent the backyard fowl issue to its planning and zoning committee to come up with a set of rules.
Clayton has had no real ordinance forbidding chickens but has recently voted to change their "Possession of Domestic Fowl- Maintaining an Enclosed Pen" portion of its zoning regulations Section 210.280 "animals running at large" and section 220.020 "nuisances affecting health".
The meeting minutes for September 24th where this came to a vote are not yet online and as far as I was able to determine, some of the zoning change has to do with secondary structures (coop) and distance from property lines. But the minutes should be approved this week so we'll know more then.