The Princess Pat Stakes was an American Thoroughbred horse race first run in 1937 at Chicago's Washington Park Race Track. A race for two-year-old fillies, except for 1941 and 1942 when it was open to fillies and mares age three and older, the Princess Pat Stakes was moved to Arlington Park in 1958.For most of its duration, the Princess Pat Stakes offered the largest purse of an American race for two-year-old filies.