Missouri Valley Iowa city park

Stayed there all summer late 80's. It was actually the fairgrounds but it served a purpose. It had a showers and restrooms. Neither were kept up and vandals liked to pull the toilet paper from the rolls but those of us staying there managed to get showers especially if they were cleaned on a particular day!
At the time it was a free will donation to the city and we were told 5.00 was the expected donation for that time.
There is also Wilson Island State park not far from there and it is pretty nice as I recall.