I know we've got a few members in Iowa, so I wanted to share my experience with getting two of my trikes legal to ride in public parks.
I live in the country and have a tiny acreage that I can ride on, but I can ride all my trails in about 2 minutes, and the rest is just gravel roads, so it gets old. We've got a handful of ATV parks (in Iowa, they use the term Off-Highway Vehicles, or OHV, for some reason) here in the state, and I really wanted to be able to ride in them, so I went through the process.
Some people have described their state as 3-wheeler hostile, but Iowa law defines an ATV as having at least 3 wheels and no more than 6, so we're pretty well covered there. You have to have a title, which is the hardest part. Most of us don't have titles for our old machines.
Titling and licensing of ATV's in Iowa is handled by the DNR, so that's where I needed to start. To get a title, first, I had to fill out a form for a title, then sign an affidavit saying that to my knowledge my three wheeler had not been previously titled. It's supposed to be signed by the seller and the buyer. This presented a problem, because I bought it from somebody out of state a few years ago. In my county (Madison, where the bridges are), they were pretty relaxed about it and let me put my name in both places. In some counties you may have to invent a "seller" to sign it if you can't get in touch with the real one. Then you take the affidavit to the local sheriff or town PD, and they will run the VIN and make sure it isn't stolen. I had a funny moment where I realized I had no idea wha the history of my 250SX was, and held my breath while they called it in. It came back ok, and the deputy signed off on it. Then I went back to the courthouse, completed paperwork in hand and they provided me with a title and a tag for 2009. They don't prorate the tags. I bought it in June, and I paid full price (I think it was like 15 bucks) and it's good until December 31st.
Two weeks ago, I rode in my first ATV park, and I have to say it's worth the effort. We went to Bluff Creek in Oskaloosa Iowa, and it was a blast. We're planning to visit all the parks within 2 hours of us in the next few months. The DNR guy came over and checked our tags, and commented that they don't see many three wheelers around, then reminisced about his dad's 3-wheeler back in the day. I got quite a few looks, but I couldn't tell if it was because seeing the trike itself was so unusual, or the fact that my riding buddy was on a near-new KTM 450 dirt bike and we made such a strange pair! He whomped me severely on the MX track and open trails, and I bested him on the mudhole-laden perimeter trails. I should have brought my camera!