Before Long Island's Parrish Art Museum breaks ground on a 37,300-sq.-ft. expansion early next year, a must-see show, “American Landscapes: Treasures From the Parrish Art Museum,” displays some 50 paintings, about half by artists who lived or worked on Long Island. From Asher B. Durand to April Gornick, Samuel Colman to William Merritt Chase, the collection's strengths are shown in masterpieces of Tonalism and some fine contemporary works...