Off U.S. 20 in Dyersville, you can park in the Super 8 parking lot (if it's not full, you can get about 12 to 15 trucks in there). Right next-door is the National Farm Toy Museum. It has a lot of toy farm equipment from through the years, and a huge display of toy semi trucks. It takes 3-4 hours to completely go through the museum. If you have time, you can drop your trailer and go about four miles north of town to the Field of Dreams where the movie was filmed. There's a excellent restaurant right next to the Super 8.
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