I grew up in the northwest corner of Iowa close to Lake Okoboji and lived there for 22 years. I enjoy going back to visit but do not like the snow. It's a lot slower lifestyle than metro Atlanta and is quite refreshing. I think that's great that you want to photograph the courthouses. Keep us posted on your travels. The Clay County Fair (the world's largest county fair) occurs in September for 10 days.
Unfortunately, I did not start camping until I moved south to Georgia. I can check with my nephew who has a TT to see if he has some CG recommendations. However, I will be eager to hear what others have to say as well. We have been "toying" with the idea of towing our TT up there for our next visit and making a larger trip out of it.