St. Louis County, MO Animal Ordinances: Dog Leash Laws (2026)

200 of the County's Animal Control Code puts the leash duty on 'every person responsible' for a dog, cat, or other animal, not just the animal itself. An animal is legally 'at large' the moment it is outside a cage or building it cannot escape unless it is on a leash held by someone capable of controlling it, inside a vehicle that is parked, stopped, or being driven, or physically on the property of the person responsible for it. Dogs and cats in heat get a stricter definition: they count as confined only if kept inside the residence where they cannot escape or be reached by other animals, or on a leash on the owner's property under direct supervision.

Any other animal is at large whenever it is off its owner's property and not caged or under a capable handler's control. The ordinance carves out narrow exceptions: hunting and field-trial dogs and dog-show entrants on designated land, tracking dogs used in police activities, canine-corps dogs for any municipal, county, state or federal law enforcement agency or the military while on official duty, and trained service animals accompanying the person they assist, provided that person carries the training school's identification card. 240: a sexually neutered animal's owner faces a $25 fine for a first offense within twelve months, $100 for a second, $200 for a third or fourth, and $500 for a fifth or later offense referred to the county counselor.

If the animal has not been sexually neutered, the fines double to $50, $200 (with half waivable on proof of later sterilization), $500, and $1,000, respectively. The rule applies in unincorporated St. Louis County and in municipalities that have not adopted their own conflicting leash ordinance.