Illinois State Forest preserves also had full prohibition on mushroom picking. This has changed and it is now allowed. Hopefully this change will trickle down to county forest preserves.
I wouldn't hold my breath about this, considering the liability issues. I assume that the rapidly worsening funding crisis in the state-owned parks led to the rescinding of the prohibition, simply because there aren't nearly enough personnel to police it.
In a marginally related matter, never listen to a know-it-all visiting out-of-state Grandma re: 'shroom picking. Yikes:
Trust me, kids - I'm an Educator!