Humans:
* William Nack: The author and narrator of the book, a racing writer for Sports Illustrated.
* Penny Chenery: The owner of Secretariat, daughter of Meadow Stable founder Christopher Chenery.
* Lucille Chenery: Penny's mother, a crucial figure in the family's decision to keep Meadow Stable afloat after Christopher's illness.
* Meadow Stable: The family who owned Secretariat.
* Louise Tweedy: Penny's long-time friend and confidante.
* John Tweedy: Louise's husband, a key figure in the management of Meadow Stable.
* Frank "Pancho" Martin: The lead trainer of Secretariat, a colorful and determined figure.
* Ronnie Turcotte: The jockey of Secretariat, a skilled and brave rider.
* Bud Delp: The assistant trainer of Secretariat, working closely with Frank Martin.
* Dr. Alex Harth: The veterinarian for Meadow Stable, particularly for Secretariat.
* Jim Gaffney: The head of the Meadow Stable farm, responsible for the care of the horses.
* Jack Van Berg: A rival trainer, particularly with Frank Martin.
* Eddie Arcaro: A legendary jockey, briefly involved in Secretariat's early career.
* The "Big Red" team: The people who worked directly with Secretariat, including grooms, exercise riders, and stable hands.
Horses:
* Secretariat: The titular character, a legendary racehorse known for his speed and grace.
* Rags to Riches: Secretariat's stablemate and rival.
* The other horses: Various other horses from Secretariat's era, including his rivals like Sham and Riva Ridge.
This list is not exhaustive. The book features a vast array of supporting characters, including other owners, trainers, jockeys, and even journalists who followed Secretariat's career.
It's important to note that the book primarily focuses on Secretariat's story, and some characters receive more attention than others. However, all of these individuals play a role in shaping the narrative and providing context for Secretariat's incredible journey.