In the 1890s visitors from New York's Art Students League journeyed to the Cos Cob section of Greenwich to take classes taught by American impressionist John Henry Twachtman at a boardinghouse for artists and writers run by Josephine and Constant Holley. Thus the Cos Cob art colony, which flourished until 1920, was born. Today the 1730-vintage house is the Bush-Holley Historic Site, which...