Cedarmere, in the village of Roslyn Harbor, is one of the most picturesque and historic spots on Long Island's North Shore. Its main house was the country home of William Cullen Bryant, the nation's first significant poet and an influential editor of the New York Evening Post. Bryant, who ultimately owned almost 200 acres containing 13 houses, created what may be the first of Long Island's Gold Coast estates. The story of Cedarmere's buildings, grounds,...