Screaming or howling in Woodbury County, Iowa

In the summer of 1970 being young and still interested in kissing the girls I had a unique experience. We were riding around in my 1962 chevy convertible with the top down. On the edge of town there was a park, Stone State Park, consisting of 1132 acres surrounded by farms and overlooking the big Sioux River, dividing Iowa and South Dakota. We decided to go to lookout point at the park and park for a while. It was a beautiful summer night and just light enough to see in the dark. When we got there the girl I was with and I decided to take a blanket and place it on a flat spot about 20 or 30 feet from the edge of the parking lot overlooking the river. To one side of where we placed the blanket there were trees and bushes. The other couple were in the back seat of the car with the top down. We had perhaps been there for no more that 15 minutes or so and I was on the blanket kissing when all of a sudden there was something in the bushes beside us screaming down at us at the top of her lungs. The volume was mind blowing. As we were running the scream seemed to still be directed toward us. I didn’t even open the door of the car, I just jumped in and I think the girl with did the same. Although we were only kissing, almost right away and for about 35 years, I believed it had to do with babies. For all that time I was thinking she screamed at us because it was the wrong time of year for us to even think about such a thing, and thus got screamed at. Untill now. Recently captiankillmore put a link to sightings on the forum. When I went and read it, I think I may have found the answer to my thinking babies all these many years. At the time and for about 35 years it was just a sixth sense feeling. Her scream as it went on sounded just like a human women, except louder with unbelievable volume.