North America's Top 10 (post civil war - in foal year order)
Qualification: Commenced racing in USA
In the race summary grade 1 wins appear in brackets. 'G1L' means that race was given grade 1 status when the grading system was introduced in North America in January 1974 with the publication of the first list of 330 North American Graded Stakes by 'Bloodhorse' (see Thoroughbred Owners and Breeders Association: TOBA.)
Horse racing in North America effectively ceased due to the following disruptions:
1861-1865: American Civil War
1894: New Jersey legislature banned parimutuel gambling.
1908-1913: New York State legislature passed the Hart–Agnew anti-gambling bill. Owners, whose horses of racing age had nowhere to go, began shipping them and their trainers to England and France. Thoroughbred Times reported that more than 1,500 American horses were sent overseas between 1908 and 1913 and that at least 24 were either past, present, or future Champions.
Miss Woodford (USA) 1880 (mare) USD 118,270 48 starts: 37 wins (3 x G1L), 7 seconds, 2 thirds. Win % 77.1, Place % 95.8.
Miss Woodford was the first North American horse to win USD 100,000 in North America. Unlike many North American mares she competed regularly against the males. She had a winning streak of 17 from September 1883 to June 1885 if a heat win is included (streak of 16 if heat win is excluded). Her win rate of 77.1% for a horse that started 48 times was exceptional. Her win rate is greater if her two heat wins are included in the total starts and wins. The only mare in my top 10 (or 20).*
Man o' War (USA) 1917 USD 249,465 21 starts: 20 wins (6 x G1L, 1 second, 0 thirds. Win % 95.2, Place % 100.0.
Man o' War won the two horse Lawrence Realization Stakes at Belmont Park NY over 13 furlongs by 100 lengths in world record time, effectively a solo world record run. Over his two-year career, Man o' War won 20 of 21 races, setting three world records, two American records, and three track records. In his only defeat many blamed the starter for not waiting until all horses were lined up behind the strand.
War Admiral (USA) 1934 USD 273,240 26 starts: 21 wins (5 x G1L), 3 seconds, 1 third. Win % 80.8, Place % 96.2.
War Admiral won the 3YO triple crown and came back as a 4YO to win important races including New York's prestigious Jockey Club Gold Cup over 2 miles.
Citation (USA) 1945 USD 1,085,760 45 starts: 32 wins (10 x G1L), 10 seconds, 2 thirds. Win % 71.1, Place % 97.8.
Citation won 10 races later classified at grade 1 including the 3YO triple crown and New York's prestigious Jockey Club Gold Cup over 2 miles as a 3YO. He was first horse to win USD 1,000,000.
Nashua (USA) 1952 USD 1,288,565 30 starts: 22 wins (12 x G1L), 4 seconds, 1 third. Win % 73.3, Place % 90.0.
Nashua won 12 races later classified as grade 1. Only beaten by champion Swaps in the Kentucky Derby he got revenge in a match race winning by 6.5 lengths. Won New York's prestigious Jockey Club Gold Cup over 2 miles twice with the second win in American record time. Retired as world's leading money winner.
Round Table (USA) 1954 USD 1,749,744 66 starts: 43 wins (9 x G1L (6 x dirt, 3 x grass)), 8 seconds, 5 thirds. Win % 65.2, Place % 84.8.
Round Table was as tough as nails winning 43 of 66 starts in just 4 years and a champion on both dirt and grass, a rare feat. Retired as world's leading money winner.
Buckpasser (USA) 1963 USD 1,462,014 31 starts: 25 wins (12 x G1L), 4 seconds, 1 third. Win % 80.6, Place % 96.8.
Buckpasser raced from age 2 to 4. As a 4YO Buckpasser competed for headlines with the star 3YO's Damascus and Dr Fager considered two of the all time greats. Buckpasser and Damascus both won New York's prestigious Woodward Stakes and Jockey Club Gold Cup as 3YOs. Despite Damascus beating Buckpasser by 10 lengths in the 1967 Woodward Stakes (Dr Fager 3rd) in a race sometimes described as the race of the century I have given the nod to Buckpasser as he won more 3YO+ races later classified as grade 1 (5 versus 3 each to the others) and had a superior big race record with 12 wins that were later classified as grade 1.
Secretariat (USA) 1970 USD 1,316,808 21 starts: 16 wins (7 x G1), 3 seconds, 1 third. Win % 76.2, Place % 95.2.
Just for the incredible 1973 Belmont Stakes vision on youtube for those that never watched him race.
Affirmed (USA) 1975 USD 2,393,818 29 starts: 22 wins (14 x G1), 5 seconds, 1 thirds. Win % 75.9, Place % 96.6.
Affirmed raced from 2 - 4 years winning grade 1 races each year including the 3YO triple crown. Alydar, his great rival at 2 and 3 years, beat him in three occasions but ran second to him on six occasions including the triple crown races. They never met at 4 when Alydar's best was a grade 3 win. Retired as world's leading money winner.
Spectacular Bid (USA) 1976 USD 2,781,608 30 starts: 26 wins (13 x G1), 2 seconds, 1 third. Win % 86.7, Place % 96.7.
A middle distance flying machine. Won his final race the grade 1 Woodward Stakes in a walkover and I can't imagine that will happen again. Retired as world's leading money winner.
*The first two of the modern grade 1 races for 4YO+ horses did not commence until 1884 and Miss Woodford did not compete in either of them which is the reason she did not win a race later classified as grade 1 after her three year old year.
The Suburban Handicap (then run at Sheepshead Bay, NY, later Belmont Park, NY) and the Monmouth Hcp (run at Monmouth Park, Oceanport, New Jersey, not run 1894-1945; later named Amory L. Haskell Hcp from 1967 then Philip H. Iselin Stakes) were the first modern grade 1 races for older horses when they commenced in 1884.
I note that the Monmouth Hcp is recognised as the forerunner of the modern grade 1 race when the Monmouth Park track was re-opened on a new site some 50 years after the original track closed.
Some notable omissions:
Seabiscuit (USA) 1933
Interestingly Seabiscuit fell out of favour with the editors of Daily Racing Form in the 1970's (see various editions of the American Racing Manual) and was deleted from their list of 'greats' for a number of years.
Tom Fool (USA) 1949
Native Dancer (USA) 1950
Swaps (USA) 1952
Bold Ruler (USA) 1954
Kelso (USA) 1957
Damascus (USA) 1964
Dr Fager (USA) 1964
Forego (USA) 1970
John Henry (USA) 1975
Cigar (USA) 1990
Curlin (USA) 2004