The note on the reverse indicates the carriage passengers are Mr. and Mrs. Phelan Beale, or Edith Ewing Bouvier Beale "Big Edie" and her then-husband Phelan Beale, who would have still been married and living at Grey Gardens (purchased in 1923) when this picture was taken in 1926. Phelan and Big Edie separated in 1931 and divorced in 1946. Robert Dayton loaned the Jerusalem Dilly, created in 1824, for this party for the East Hampton Riding Club, which seems to have involved some sort of pageant dress.