North of New York City on New York’s Route 9 the driver will be rewarded with an astonishing array of historic houses open to the public. Presidents’ homes, palaces of the Gilded Age, and artists’ studios are thick on scenic outlooks along the Hudson River. In May, just as spring reaches its glory on the river, two new house museums will open their doors, gilding—if that’s even possible—the lily. Owned by the National Trust for Historic Preservation and managed by Historic Hudson Valley, caretaker of many of the great Hudson River properties, Nelson A. Rockefeller’s eighty-seven-acre estate and forty-room turn-of-the-century stone mansion in North Tarrytown is ready for visitors, the first time any Rockefeller home has allowed the public in.