 Princequillo was the Leading sire in North America for 1957 and 1958 and Leading broodmare sire from 1966 through 1970 and again in 1972 and 1973.Among his daughters' progeny are Mill Reef, Fort Marcy, High Echelon, Triple Crown winner Secretariat, and Secretariat's chief rival Sham.His son Prince John was Leading broodmare sire in 1979, 1980, 1982 and 1986.