When Secretariat crossed the finish line 31 lengths in front at the 1973 Belmont Stakes, it broke a 25-year Triple Crown drought, then the longest hiatus between Triple Crowns since Sir Barton first accomplished the feat in 1919. A few months previously, Secretariat had already been syndicated for stud duty at Claiborne Farm for a then-record valuation of a little more than $6 million. Despite his record syndication and considerable success as both a sire and broodmare sire, Secretariat was not the best sire of his crop. And in fact, although Secretariat was without doubt the champion of his crop because of his relentless ability to sustain his gallop over a distance of ground, in terms of sheer speed, he was not even the fastest horse in his crop. Both of those retrospective honors belong to Mr. Prospector, who was also the highest-priced horse at the 1971 Keeneland July sale of selected yearlings. Secretariat’s legacy as a sire lives on mostly through his maternal grandsons A.P. Indy and Storm Cat, but Mr. Prospector now stands at the head of the most successful classic sire line in the United States. His fifth-generation male-line descendant American Pharoah, who broke a 37-year Triple Crown drought with his Belmont Stakes victory on June 6, is the 32nd American classic winner descending in male line from Mr. Prospector dating back to when his son Conquistador Cielo won the Belmont in 1982. Purchased for $220,000 at the 1971 Keeneland July sale by trainer Jimmy Croll on behalf of Abraham I. Savin, Mr. Prospector was unraced at 2 but briefly flattered as a Triple Crown prospect himself early in his 3-year-old season. Mr. Prospector set a Gulfstream Park six-furlong track record of 1:07.80 in his second start, a record that stood for 26 years until his great-grandson Artax broke it in the 1999 Breeders’ Cup Sprint (1:07.66). Jimmy Croll took Mr. Prospector to Churchill Downs in hopes of running him in the Kentucky Derby, but he was beaten by Settecento in a Derby Trial run in 1:37 for the mile, and the ankle problems that plagued his racing career forced abandonment of that idea. Mr. Prospector proved his speed again as a 4-year-old, winning the Gravesend Handicap, and he set another six-furlong track record when he won the Whirlaway Handicap at Garden State in 1:08.60. But he was beaten comfortably by Forego, who was then developing into the second-best racehorse of the crop, in the Grade 2 Carter Handicap. Mr. Prospector broke down again shortly thereafter and retired with a record of 7 wins in 14 starts and earnings of $112,171. As indicated by his yearling price, Mr. Prospector possessed pedigree and conformation good enough to stand anywhere, and several farms in Kentucky would have gladly taken him, but Savin owned a farm in Ocala, Fla., and preferred to stand him there. Mr. Prospector was by champion 2-year-old and proven classic sire Raise a Native. Mr. Prospector’s dam, Gold Digger, by Prince John, was the equivalent of a modern Grade 3 winner from the great family founded by Myrtlewood. A medium-sized, long-bodied horse who turned out in his right front a bit, Mr. Prospector was perfectly balanced with the long hip and deeply sloped shoulder of the high-class Thoroughbred. Mr. Prospector’s first crop, foaled in 1976, included 1978 champion 2-year-old filly It’s in the Air, and his second was headed by Grade 1/Group 1 winners Fappiano and Hello Gorgeous. Those top-level performers inevitably attracted multi-million-dollar bids from Kentucky, and in 1980 he was syndicated and moved to Claiborne Farm, where he stood for the rest of his career. When the progeny of the better mares available in Kentucky came to the races, Mr. Prospector became leading sire in 1987 and 1988. In retrospect, the most remarkable thing about Mr. Prospector’s stud career is not the 181 stakes winners, the 16 champions, the 46 Grade 1/Group 1 winners, or even his own three classic winners, Conquistador Cielo, Tank’s Prospect, and Fusaichi Pegasus. The most remarkable aspect of his 25-year career as a stallion is evident in the accompanying table, which delineates the 32 American classic winners descending in male line from Mr. Prospector. Those classic winners trace their lineage to Mr. Prospector through 12 different sons. By comparison, Northern Dancer, whose male line is more prolific globally and who stands second to Mr. Prospector in classic-winning descendants in the era, is responsible for 17 classic winners through eight sons. Eleven of those 12 sons with classic-winning descendants were conceived during Mr. Prospector’s years in Kentucky, but by far the most prolific classic line descending from Mr. Prospector comes through his Florida-conceived and -bred son Fappiano. Bred and raced by John Nerud out of the Dr. Fager mare Killaloe, Fappiano was markedly offset in front but won the 1981 Grade 1 Metropolitan Handicap before retiring to Tartan Farms in Ocala. Like his sire, Fappiano had early success which soon attracted Kentucky bidders, and he finished his relatively brief stud career at Lane’s End. Like Mr. Prospector, though, he had conceived his most important son in Florida, 1990 Kentucky Derby winner Unbridled. Bred and raced by Frances Genter, Unbridled stands at the head of two remarkable sequences of classic runners. His first-crop son Grindstone won the 1996 Kentucky Derby and sired 2004 Belmont Stakes winner Birdstone. Birdstone, in turn, sired 2009 Kentucky Derby winner Mine That Bird and 2009 Belmont winner Summer Bird. That makes four consecutive generations of classic winners from the Unbridled branch of Mr. Prospector. Unfortunately that sequence is likely at an end since Mine That Bird is a gelding, and Summer Bird, whose first foals are 3-year-olds, stood only two seasons in America and died after standing one more season in Japan. Unbridled also stands at the head of another line that came very close to producing four consecutive Kentucky Derby winners. His son Empire Maker ran second on a troublesome hoof in the 2003 Derby before winning the Belmont, and he sired 2009 Derby runner-up Pioneerof the Nile, sire of 2015 Triple Crown winner American Pharoah. Since Coolmore Stud purchased the breeding rights of American Pharoah for a reported $8 million, he will obviously have an excellent chance of extending the classic reign of the Unbridled branch of Mr. Prospector. The Smart Strike, Seeking the Gold (through England-based Dubawi), Machiavellian, and Forty Niner branches of Mr. Prospector also have obvious chances of expanding the empire, and the Kingmambo branch is highly successful in Japan through his leading sire son King Kamehameha. Remarkably, Mr. Prospector was even more dominant as a broodmare sire than as a sire of runners, leading the American broodmare sire list nine times. Still, it is as a sire of sires that Mr. Prospector made his most important contribution. In addition to the 12 classic lines enumerated in the accompanying box, Mr. Prospector’s sons Miswaki, Crafty Prospector, Straight Strike, Damister, Fast Gold, Lode, Jade Hunter, Carson City, Golden Voyager, and Hussonet, among others, all made important contributions to the Thoroughbred somewhere on the globe. It is perhaps fair enough to say that American Pharoah’s Triple Crown is the culmination of 40 years of development of what has become the principal American classic line from the progeny of a horse whose major victories were at six furlongs and who never won beyond seven furlongs. Whether Mr. Prospector could have stayed beyond sprint distances had he stayed sound enough can never be known. His legacy in the American classics, however, certifies for all time that the classicism in his pedigree was still there in his genes. Although Secretariat was the dominant classic horse of his generation, it is Mr. Prospector who has become a true American classic.