Complex sentence: Drayton Hall is managed by the National Trust for Historic Preservation, which opened the house to the public in 1977 and presents both sides of the historic plantation economy exemplified by the Draytons, both white and black.
Split into simpler sentences: Drayton Hall is managed by the National Trust for Historic Preservation, which opened the house to the public in 1977. It presents a full interpretation of the historic plantation economy as exemplified by the Draytons, both white and black.