Yes, it is absolutely legal to leave your stand up on public ground in Illinois; it just has to have a tag affixed displaying the hunter's name and contact info, and must be taken down by Jan. 15.

Your situation revolves around the fact that shotgun season opens in Illinois this weekend. I saw a new stand up this past week in an aread I've been hunting all year, with no sign that anyone else was present until that. I remarked about my stand getting stolen this past week, and I believe that had a lot to do with it... the "orange army" preparing to invade. Most of the time, the woods is mine. This time of the year, however, is a different story.