Edward Hopper has been celebrated for over half a century as America's most eloquent realist artist. His best known oils, such as Nighthawks , Early Sunday Morning , and House by a Railroad , are powerful psychological statements that convey a sense of angst and alienation. Yet there is another Hopper we know less well: the freer, more spontaneous spirit that emerges in his watercolors. In 1923 he spent a summer in Gloucester, Massachusetts, and began...