Sayajirao (1944–1965) was a British Thoroughbred racehorse.
 A full brother to 1945 Epsom Derby winner, Dante, he was out of the mare Rosy Legend and sired by the great Nearco who is described by "Thoroughbred Heritage" as "one of the greatest racehorses of the Twentieth Century" and "one of the most important sires of the century."
 Nearco was not only unbeaten in racing, but also the patriarch of the most dominant sire line in Thoroughbred history.
Bateau (born 1925) was an American Thoroughbred Champion racehorse and a daughter of Man o' War and out of the French mare Escuina.
Kelso (April 4, 1957 – October 16, 1983) was an American thoroughbred race horse considered among the best racehorses in history.
 In the list of the top 100 U.S. thoroughbred champions of the 20th Century by The Blood-Horse magazine, Kelso ranks 4th, behind only Man o' War (1st), Secretariat (2nd) and Citation (3rd).
 In his long career, Kelso defeated many leading Thorougbred racehorses including Carry Back, Gun Bow, Bald Eagle, Tompion, Never Bend, Beau Purple, Quadrangle, Roman Brother, Crimson Satan, Jaipur, Ridan and Pia Star, as well as other top thoroughbreds, often conceding weight under handicap conditions.
 In doing so, Kelso beat more champions and Hall of Fame horses than any other thoroughbred racehorse in the 20th Century.
Tom Fool (March 31, 1949 – August 20, 1976) was an American Thoroughbred racehorse, a winner of the American Horse of the Year award and a Hall of Fame inductee.
 He sired the outstanding racehorses Buckpasser and Tim Tam.
Havre de Grace (foaled on May 12, 2007, in Kentucky) is an American Thoroughbred Racehorse who was 2011 American Horse of the Year.
 During her racing career, she was owned by Fox Hill Farms and trained by J. Larry Jones.
 Her sire is the 2005 American Horse of the Year, Saint Liam.
 Her dam is the mare Easter Bunnette, a daughter of Carson City.
 Her name derives from the city and racetrack of Havre de Grace, Maryland.
Man o' War (March 29, 1917 – November 1, 1947) was an American Thoroughbred who is widely considered one of the greatest racehorses of all time.
 During his career just after World War I, he won 20 of 21 races and $249,465 in purses.
 He was the unofficial 1920 American Horse of the Year and was honored with Babe Ruth as the outstanding athlete of the year by "The New York Times".
 He was inducted into the National Museum of Racing and Hall of Fame in 1957.
 On March 29, 2017, the museum opened a special exhibit in his honor, "Man o' War at 100".
General Assembly (1976–2005) was an American Thoroughbred racehorse.
 He was bred and raced by the prominent husband-and-wife team of Bertram and Diana Firestone, of Upperville, Virginia.
 General Assembly was out of the mare Exclusive Dancer, daughter of Hall of Fame inductee and American Horse of the Year Native Dancer.
 His sire was the 1973 U.S. Triple Crown champion Secretariat, who was rated #2 in the Blood-Horse magazine List of the Top 100 U.S. Racehorses of the 20th Century.
Gun Bow (1960 – December 1979) was an American Thoroughbred racehorse.
 He was one of America's leading older male racehorses in 1964 and 1965 and was later inducted into the Hall of Fame.
 Gun Bow was noted for his rivalry with five-time American Horse of the Year Kelso.
Game On Dude (foaled April 26, 2007 in Kentucky) is a retired American Thoroughbred racehorse gelding.
 He won fourteen graded stakes races, including eight Grade I stakes: the Santa Anita Handicap in 2011, 2013, and 2014 the only horse to have won that race three times; he also won the Goodwood Stakes twice (2011, 2012), the 2013 Pacific Classic Stakes, and the Hollywood Gold Cup twice (2012, 2013).
 He has beaten many of the leading North American racehorses including Awesome Gem, Tizway, Ruler on Ice, Uncle Mo, Stay Thirsty, Mucho Macho Man and Will Take Charge and has been rated among the best thirty racehorses in the world in the annual World Thoroughbred Rankings.
 Upon his retirement, he was compared favorably as one of the greatest racing geldings of all time, along with Kelso, John Henry and Forego.
California Chrome (foaled February 18, 2011) is an American Thoroughbred racehorse.
 He was named the 2014 and 2016 American Horse of the Year.
 He won the 2014 Kentucky Derby, the Preakness Stakes, and the 2016 Dubai World Cup.
 In 2016, he surpassed Curlin as the all-time leading North American horse in earnings won.

Question: Which Racehorse was the daughter of the American Thoroughbred was the unofficial 1920 American Horse of the Year, considered one of the greatest racehorses of all time?
Answer: Bateau