Complex sentence: Her father was architect Thomas R. Johnson who worked in the firm of Cass Gilbert the architect of several noteworthy buildings in New York City including especially the Woolworth Building, the New York Customs House, and library buildings.
Split into simpler sentences: Her father was architect Thomas R. Johnson who designed several noteworthy buildings in the New York City. Among these include the Woolworth Building, the New York Customs House, and library buildings.