Complex sentence: One aspect of the plan was a Fall Frolic held on September 25,1920 which had a very popular event, a parade of young women pushed along the boardwalk in rolling chairs.
Split into simpler sentences: One aspect of the plan was a "Fall Frolic" held on September 25,1920. One of the most popular aspects of the "Fall Frolic" was a parade of young women pushed along the boardwalk in rolling chairs.