Seattle Slew, the only horse to win the Triple Crown while undefeated, died Tuesday morning in his sleep at Hill 'n' Dale Farm near Lexington. On May 7, 1977, exactly 25 years ago, Slew won the Kentucky Derby. Seattle Slew had been the last remaining Triple Crown winner, and his passing leaves the Thoroughbred world without a living Triple Crown winner for the first time since Sir Barton first accomplished the feat in 1919.Sold at auction for $17,500, Seattle Slew became not only a great racehorse but one of the most important sires in Thoroughbred racing history. He has sired 102 stakes winners, including A.P. Indy, Slew o' Gold, Surfside, Swale, Capote, Landaluce, Slew City Slew, Flute, and Honest Lady."He was the most complete Thoroughbred the industy has ever seen," said Mickey Taylor, who raced the horse with his wife, Karen, and Dr. Jim Hill and his wife, Sally. "He just kept raising the bar with every record he broke." The Taylors were with him at the time of his death, having attended to Slew throughout his career. "He had the greatest heart; he was a fighter to the end." Karen Taylor said.Grooms Tom Wade and Carlos Arreola also were with the horse. Wade started caring for Seattle Slew when the stallion began his stud career at Spendthrift Farm near Lexington.Slew had recently been moved to Hill 'n' Dale from Three Chimneys Farm near Midway, Ky., following his second spinal surgery. His barn at Three Chimneys was too close to the breeding shed, causing him to become agitated when mares arrived on the farm.John Sikura, the owner of Hill 'n' Dale Farm, said, "It was one of the great privileges to be around something great, a feeling that will likely never be duplicated. But with extreme reward comes extreme sadness. To be near greatness is what everyone in this business aspires to, and it happens so rarely. He was one in a million, and showed us there is that possibility in a game of impossibilities."Seattle Slew will be bured at Hill 'n' Dale beneath a statue in a courtyard.