sentences:  In 1961, the Whitney began seeking a site for a larger building.In 1966 it settled at the southeast corner of Madison Avenue and 75th Street on Manhattan's Upper East Side.The building, planned and built 1963–1966 by Marcel Breuer and Hamilton P. Smith in a distinctively modern style, is easily distinguished from the neighboring townhouses by its staircase façade made of granite stones and its external upside-down windows.