Complex sentence: The West Philadelphia Streetcar Suburb Historic District is an area of West Philadelphia listed on the National Register of Historic Places because it represents the transformation of Philadelphia's rural farmland into urban residential development, made possible by the streetcar, which provided easy access to Center City.
Split into simpler sentences: The West Philadelphia Streetcar Suburb Historic District is an area of West Philadelphia listed on the National Register of Historic Places. It represented the transformation of Philadelphia's rural farmland into urban residential development, made possible by the streetcar, which provided easy access to Center City.