Kane County requires that all letterboxes be registered with them. There are 20 preserves that are approved for the placement of letterboxes:

Aurora West
Burnidge & Paul Wolff Campground
Blackberry Maples
Big Rock
Bliss Woods
Campton
Dick Young
Elburn
Fabyan
Freeman Kame
Fox River Bluff and Fox River Bluff West
Hampshire
Hannaford Woods - Nickles Farm
John J. Duerr
LeRoy Oaks (currently full)
Oakhurst (currently full)
Pingree Grove
Rutland
Raceway Woods
Tekakwitha Woods

No more then 5 letterboxes/geocatches are allowed in any one preserve. To register a letterbox, you must print and fill out the application providing contact information and details reguarding where you would like to place the box. If your box is approved, an official from the county will accompany you to place the box. You must then provide evedence of periodic maintaince of the box and reapply for registration yearly. For more information on the regulations as to where boxes can be placed along with the application for registration and maps of all of the above preserves, please go to: http://www.kaneforest.com/recreation/geocaching.aspx