 In 1954 and 1955, during the first of two John Simon Guggenheim Fellowships, he carried out the research that underlay "The Japanese Influence in America" (1963); a second Guggenheim, in 1963 and 1964, supported research on the architecture of Kentucky.In 1966, Parks Commissioner Thomas Hoving appointed Lancaster curator of Brooklyn's Prospect Park, Frederick Law Olmsted's landscape masterpiece, an assignment which led to his preparation of "The Prospect Park Handbook" (1967).In 1971, Clay Lancaster moved from Brooklyn to Nantucket.