Stayed during the week, not very crowded.
We spent a week at spring mill state park. The site we where at was heavily sloped, the only flat part was where they put the fire pit at. When we looked at the other site most of the shaded sites that had some privacy where also heavily sloped, the best site we found was #9. The village, twin cave tour, and trail 4 where fun. But we weren't fond of the other trails we where on, they didn't have many view but trees (which would of been better if it wasn't so hot at the time).
This state park has a very large camp ground, campers or primative. It's a large park with tons of trails and even several caves. Some caves are guided by boat. Very neat to see. Also has a pioneer village for touring along with a visitor center honoring astronaut Virgil Gus Grissom. Offers good fishing at the lake, electric motors only, but does offer trout. I would recommend this place to anyone passing through, it can get very busy on weekends.