Until yesterday, Illinois was the only state with a ban on concealed weapons in public, but now that's all over. A federal appeals court struck down the IL ban, meaning that every state in the US allows licensed gun owners to carry covered firearms.
"The theoretical and empirical evidence (which overall is inconclusive) is consistent with concluding that a right to carry firearms in public may promote self-defense," wrote Judge Richard Posner in the majority opinion on the ruling.
Illinois residents won't be able to carry their guns in public for another 6 months, until the state legislature creates a law specifying where concealed carry is permitted. Other states have laws that restrict concealed weapons in certain locations, like government buildings.