The City of Chicago requires a leash (“restraint”) on all animals outside of private property according to Chicago Municipal City Ordinance Chapter 7-12 - Animal Care & Control  . This means Chicago parks too. Making a mistake can cost you a hefty fine, along with the possibility of you, your dog, or another dog getting hurt, and possible legal ramifications.

“Each owner shall keep and maintain his animal under restraint…Any owner who violates any provision of this section shall be subject to a fine of $300.00 if the violation does not result in severe injury or death to any person or damage to another person's property.”

Note that this $300 fine is if there is no injury, death or person property damage. The fine can escalate to up to $10,000 if there is severy injury or death, and up to $1000 fine if there is personal property damage. Additional legal fees, community service and other ramifications are also possible. The bottom line is that even if your elderly or small dog seems harmless, it’s not worth the risk. Here is the full ordinance as of May 2021 outlining fees and what else it might cost you for having your dog off leash: