No camping policy, no overnight RV parking policy and no oversize vehicle guidance is published for this festival by the city, the convention and visitors bureau or the festival itself. That is not an oversight on their part. The event occupies closed streets in a downtown grid where the parking is garages and surface lots, and garages have height bars. There is nowhere to put a thirty-foot trailer, so the honest answer is that you do not bring one in.
What that leaves is a good arrangement rather than a compromise. The trailer goes to a park on the Marshfield side or elsewhere around Springfield, we set it up once, and you drive a normal car the 27 miles in. The festival runs 10am to 6pm for the static car show and then the cruise-ins take over in the evening, so it is a long day that ends with somewhere quiet to go back to.
One scheduling caution. The 2026 edition landed on the Route 66 centennial, which Springfield has a real claim to: on April 30, 1926 the city's John T. Woodruff and Cy Avery of Oklahoma proposed by telegram that the new Chicago to Los Angeles highway be numbered 66. A centennial year draws a bigger crowd than a normal one, so do not assume next year matches it in scale, and check the city's own page for dates rather than the festival's old domain, which is years out of date.
"Rented a Class C for a family trip to Silver Dollar City. The RV climbed the Ozark hills with no problem. The kids loved the bunk beds, and the pickup in Springfield was super quick."