The ordinance, approved Tuesday, will apply to areas of the county where a similar law is not in effect, Chicago Tribune reported. It will not apply in Chicago, which already has its own firearm laws.
Chicago Tribune reported the board approved the ordinance without any debate right after honoring Hadiya Pendleton, a 15-year-old girl fatally shot last week.
The rules will take effect in August and require gun owners to report to the county sheriff if they do not have their firearms for any reason, the Tribune reported.
Violating the ordinance will result in a $1,000 fine for a first offense, $1,500 for a second and $2,000 for additional violations.
Officials said they hope the new rules will reduce the frequency of straw purchases in which people legally buy guns and then sell them to criminals.
Richard Pearson, executive director of the Illinois State Rifle Association, said the rules will only impose more hardship on law-abiding gun owners.