Complex sentence: The Weeksville Heritage Center is a historic site in the New York City borough of Brooklyn that was an important 19th century free black community, whose residents established schools, churches and benevolent associations and were active in the abolitionist movement.
Split into simpler sentences: The Weeksville Heritage Center is a historic site in the New York City borough of Brooklyn. Within this community, the residents established schools, churches and benevolent associations and were active in the abolitionist movement.