Query: Who is Philadelphia's greatest architect of the later 19th century?
Context: In the first decades of the 19th century, Federal architecture and Greek Revival architecture were dominated by Philadelphia architects such as Benjamin Latrobe, William Strickland, John Haviland, John Notman, Thomas U. Walter, and Samuel Sloan. Frank Furness is considered Philadelphia's greatest architect of the second half of the 19th century, but his contemporaries included John McArthur, Jr., Addison Hutton, Wilson Eyre, the Wilson Brothers, and Horace Trumbauer. In 1871, construction began on the Second Empire-style Philadelphia City Hall.