Swinging Rings on Santa Monica Beach, California was the highlight of my pilgrimage there in the late 1970s. Twice I saw quad back somersault dismount where the only landing mat was a large group of people with upstretched arms.
Swinging rings was very popular for girls in that era. Men did “still rings” and women did “swinging rings”.
Arnold Schwarzenegger moved to nearby Venice, California to train as a body builder. This was also the birthplace of vertical skateboard.
Southern California has an amazing acrobatic history.
Gymnastics Coaching.com 