Complex sentence: The group culminated its activities with a rally on the Winnetka Village Green in 1965, where Dr. Martin Luther King, Jr. spoke to a crowd of 10,000, his first civil rights rally in an all-white suburb.
Split into simpler sentences: The group culminated its activities with a rally on the Winnetka Village Green in 1965, where Dr. Martin Luther King, Jr. spoke to a crowd of over 8,000. This was King's first civil rights rally in an all-white suburb.