Ken D Photography wrote:
There is George Rogers Clark park just outside Springfield where I've shot nudes before.

+1 to that park, I have been photographed in the nude there more than once.  Of course you always need to choose your location in any public park carefully but there are usually areas that have little to no activity at certain times of the day.

Some of the photographers I have modelled for over the years have taken the time to make friends with a few property owners, there are usually people in rural areas who will allow an occasional photo session and aren't bothered by nudity.