Final answer:
The main competitors in the 1937 Santa Anita Handicap featured in the story of Seabiscuit were Seabiscuit and Triple Crown winner War Admiral; however, War Admiral did not actually compete in the race. The confusion comes from the movie adaptation, and the actual winner was a horse named Rosemont.
Step-by-step explanation:
The 1937 Santa Anita Handicap is a significant event in horse racing history, prominently featured in the story of Seabiscuit. The main competitors in the race as discussed in Seabiscuit were the titular horse Seabiscuit himself, who was a symbol of hope during the Great Depression, and the Triple Crown winner War Admiral. However, in reality, War Admiral did not race in the 1937 Santa Anita Handicap; the confusion stems from the 2003 movie adaptation that took creative liberties and depicted an imagined race between Seabiscuit and War Admiral. Instead, the 1937 Santa Anita Handicap included other notable horses such as Rosemont, who ultimately won the race.