The Thoroughbred racing and bloodstock worlds lost a legend on Friday as Hall of Famer and breed-shaping sire A.P. Indy died of natural causes in his stall at his longtime home, Lane’s End Farm in Versailles, Ky. The son of Seattle Slew was 31. A.P. Indy, borrowing sales jargon, is often said to be the example of the rare Thoroughbred who “ticked all the boxes.” He was a regally-bred, sale-topping yearling, who lived up to that promise by becoming a classic winner and champion, then carried on his bloodline as a leading racetrack and commercial sire, with his legacy extending through multiple generations.   “A.P. Indy passed away peacefully in his stall at the Lane’s End stallion complex, the barn he called home for 27 years,” Lane’s End said in a statement issued Friday evening. “Champion A.P. Indy’s list of accomplishments range far and wide, as his legacy continues to be carried through the outstanding performances of his sons and daughters across the globe. He was the most important and popular member of the Lane’s End team, and we are deeply sorry to all who loved him as much as we did.” A.P. Indy, who was foaled on March 31, 1989, was bred in Kentucky by Lane's End's William Farish, in partnership with W.S. Kilroy. He was out of the Secretariat mare Weekend Surprise –  whose multiple stakes horses also included Summer Squall. That colt won four stakes, including the Grade 1 Hopeful as a juvenile the year A.P. Indy was born; then continued on to win four stakes the following season, including the Preakness Stakes after finishing runner-up in the Kentucky Derby. The young A.P. Indy’s active pedigree and good looks made him a star attraction at the 1990 Keeneland July yearling sale. He topped the auction at $2.9 million, going to Japan's Tomonori Tsurumaki, who campaigned him as sole owner for the majority of his career until a partnership including Lane's End joined in for his final start. Trained by Neil Drysdale, A.P. Indy won three of four starts as a juvenile in California, capped by the Grade 1 Hollywood Futurity. He continued on after the turn of the calendar to win the Grade 2 San Rafael and Grade 1 Santa Anita Derby, making himself one of the favorites for the 1992 Kentucky Derby. However, he was scratched at the eleventh hour with a quarter crack. After a brief rest, A.P. Indy returned to the races to win the Grade 2 Peter Pan Stakes. He then extended his win streak to seven with a victory in the Belmont Stakes, delivering on his classic promise. "He is probably one of the best I have ever ridden,'' regular rider Eddie Delahoussaye, who also piloted 1983 Kentucky Derby winner Gato del Sol and 1988 Preakness and Belmont winner Risen Star, told the Chicago Tribune after the race. ''I think he’d have won the Triple Crown, but we'll never know. From the first time I rode him at Del Mar, I told Neil, 'This is a racehorse!' From his stride and determination and his whole outlook, I knew he was a true athlete." A.P. Indy was rested over the summer to give his foot additional time off. He returned to the races in September, finishing fifth in the Grade 2 Molson Export Million, then third in the Grade 1 Jockey Club Gold Cup. However, those efforts set him up for a strong performance in the Breeders' Cup Classic, contested that year at Gulfstream Park. He won by two lengths over Gold Cup winner Pleasant Tap, locking up Horse of the Year honors, as well as the Eclipse Award as outstanding 3-year-old male. A.P. Indy was retired to Lane's End for the 1993 breeding season, with a career record of eight wins from 11 starts and earnings of $2,979,815. He was subsequently inducted into the National Museum of Racing and Hall of Fame in 2000, alongside Drysdale. “We wanted to keep him in training," Farish explained to Daily Racing Form at the time about the decision to retire the colt. "He’s very sound and such a brilliant horse, but it would be taking a tremendous risk with a great sire prospect. So many of our top horses have been retired to Europe or Japan that we need a horse like this to stand in the U.S. Everyone involved concluded that this was the right thing to do.” A.P. Indy, of course, proved a smashing success as a stallion – so much so that his stud fee reached as high as $300,000 in 2002, where it remained for seven seasons, until the recession that began in late 2008 impacted the bloodstock market. His progeny include 164 stakes winners worldwide, for combined earnings of $137,238,550. He ranked as North America's leading general sire in 2003, when his son Mineshaft was honored as Horse of the Year; and 2006, when his son Bernardini captured the Preakness Stakes en route to a divisional Eclipse Award. The stallion, who ranked among the leading sires on six other occasions, had another American classic winner in the Eclipse champion filly Rags to Riches, who won the 2007 Kentucky Oaks before outdueling the great Curlin for a historic Belmont Stakes victory. A.P. Indy was also the sire of Eclipse Award champions Honor Code and Tempera; Sovereign Award Canadian champions Catch the Thrill, Eye of the Leopard, Marchfield, and Serenading; UAE Horse of the Year Festival of Light; Saudi Arabian champion Sun Sprinkles; and Gabriel's Hill, a champion in Ecuador who was multiple graded placed in the U.S. A.P. Indy was represented by another Kentucky Oaks winner in Secret Status, and had Grade/Group 1 winners A. P. Adventure, A P Valentine, Aptitude, Dreaming of Julia, Flashing, Friends Lake, Girolamo, Golden Missile, Got Lucky, Indy Five Hundred, Jilbab, Little Belle, Long River, Love and Pride, Majestic Warrior, Music Note, Passing Show, Racey Dreamer, Royal Indy, Runup the Colors, Stephen Got Even, Sweet Symphony, Symboli Indy, Take Charge Indy, Telling, and Tomisue's Delight. Along with the accomplishments of his first-generation progeny, A.P. Indy built a meaningful legacy through his sons and daughters. The stallion became the most prominent modern representative of the male line of his great-great grandsire, the legendary Bold Ruler, and provided sons to carry on that line. The stallion has 29 sons still active at stud worldwide, including, in Kentucky alone, Malibu Moon, the sire of Kentucky Derby winner Orb; Bernardini, a steady producer of Grade 1 winners; the consistent stallions Congrats, Flatter, and Mineshaft; Commissioner and Honor Code, who were among last year's freshman sires; the young stallion Take Charge Indy, whose early crops were so successful that he was sought back for the Kentucky market after a brief stint in Korea; and Raison d'Etat. Mineshaft and Honor Code both stand at Lane's End. Moreover, A.P. Indy's late son Pulpit, who died in 2012, was a successful sire of racehorses, but his greatest legacy has been as a sire of sires. His son Tapit is a three-time leading general sire who holds the single-season earnings record for a North American stallion, and has sired three winners of the Belmont Stakes. Another son, the late Lucky Pulpit, sired two-time Horse of the Year and dual classic winner California Chrome. Tapit is emerging as a sire of sires in his own right, with his sons Tapizar and Flashback siring Eclipse Award champions and four sons in the top 15 on last year's freshman sire list. California Chrome, who now stands in Japan, will be represented by his first juveniles this year. Pulpit's remaining active sons at stud in Kentucky, in addition to Tapit, include, Grade 1 winners Lord Nelson, Mr Speaker, and Sky Mesa. A.P. Indy was also the leading broodmare sire of 2015, and ranked among the top broodmare sires on the continent seven other times. The best runner produced by one of his daughters has been three-time Eclipse Award champion and Hall of Fame racemare Royal Delta. She was out of A.P. Indy's stellar daughter Delta Princess, who also produced Grade 1 winners Crown Queen and Delta Prince and Grade 1-placed Carnival Court. A.P. Indy's daughters have also produced Eclipse Award champions Game Winner and Wait a While, Kentucky Oaks winner Plum Pretty, and French Oaks winner Senga, among other top-level performers worldwide. A.P. Indy was pensioned from stud duty in 2011 due to declining fertility. Through the years, Lane’s End has taken an individualized approach in ensuring the happiness of its pensioned stallions in their twilight years. Some are happiest leaving behind the activity of an active stallion barn so they don’t become stressed or frustrated by not participating in breeding sessions, as was the case with the late Gulch, who lived out his years at Old Friends; some, such as the late Kingmambo, are happy simply to be moved to a quieter area in the stallion complex. But A.P. Indy, who thrived on routine, remained in the same stall in the front barn of the Lane’s End stallion complex, going about the routine he has kept for decades, with the exception of trips to the breeding shed, and being turned out in his same paddock, which held pride of place in front of the complex’s office. He continued to be cared for by his devoted groom of well over a decade, Asa Haley. He also continued to be visited and celebrated by racing fans, and was applauded by the industry last year on the occasion of his 30th birthday. “He’ll have influenced the breed for decades to come,” Lane’s End wrote on its official blog on that occasion. “And what better tribute than that? To know that someday, young students of the game will see the name A.P. Indy, and they will think: ‘Yes. He was one of the greats. He was the stallion that built Lane’s End.’”