Majestic Prince
He set up a racing stable in California with U.S. Racing Hall of Fame jockey-turned-trainer Johnny Longden. Among the horses they raced was the great Majestic Prince whose important stakes include the 1969 Kentucky Derby and Preakness Stakes. Majestic Prince was inducted into the National Museum of Racing and Hall of Fame in 1988 and was listed at No. 46. in The Blood-Horse magazine ranking of the top 100 U.S. thoroughbred champions of the 20th Century. In 1975, McMahon had another Triple Crown contender with Diabolo who finished third in both the Kentucky Derby and Preakness Stakes, and was fourth in the Belmont Stakes.