Amassed over four decades by Jonathan (Jack) Westervelt Warner, the former chief executive of Gulf States Paper Corporation (now the Westervelt Company), the selection includes masterworks by the leading American artists of the 19th and 20th centuries, including Albert Bierstadt, William Trost Richards, Childe Hassam, Frederick Carl Frieseke, Marsden Hartley, Thomas Hart Benton, Charles Ephraim Bu