Screaming or howling in Clayton County, Iowa

This is an old report, but recently after watching the better bigfoot programs on tv, it dawned on me that what we had experienced was a bigfoot. Every September, my husband I would go hiking to see the color. This trip was in September, 1970 to Pikes Peak State Park located on the highest bluff on the Mississippi River in Iowa. September is a time when the kids are back in school. There was only one other car in the parking lot so the trails were deserted. Pikes Peak had several walking trails. We decided to take the longest which led to the overlook on the Mississippi. We had hiked almost to the point of the overlook. Fall had us crunching on the fallen leaves when we heard a large thump, thump, thump from behind the trees followed by a loud animal scream that we had never experienced before. Having hiked in the woods almost weekly, we learned to identify most of the animal sounds around us. This was not an identifiable animal. The screech scared us so badly that we immediately turned around and ran as fast as we could all the way back to the rangers station. Having reached the station we immediately inquired about the animal we had encountered. We explained in great detail what had happened, but the rangers said they had no clue what we had encountered and that nothing similar had ever been reported. To this day I am still haunted by the sound of the footsteps and the screech. Until the bigfoot programs I had never considered that what we had encountered could be a bigfoot. Now I'm 90% sure of my identification. I also noticed that there were no other sightings in the same area. Perhaps we were just at the right time and the right place, but I know what we experienced. Although late, previously I was unaware of any reporting sites to relay our experience. I am excited to hear your thoughts.