Jarret is a 13-year-old enslaved boy living at The Meadows in Lexington, Kentucky. He possesses a profound understanding of equine behavior, preferring the company of horses over human interaction. Born to an enslaved mother and a free father, he benefits from his father's expert instruction in horse training. He quickly distinguishes himself through his gentle, intuitive approach to socializing the notoriously aggressive bloodlines of the estate's horses.

Theo is a PhD candidate in Art History at Georgetown University. Raised in international diplomatic circles by his Nigerian mother and American father, he developed a passion for equestrian sports early in life. He previously played star-level polo at Oxford before abandoning the sport due to relentless racial harassment. He directs his academic focus toward recovering the ignored history of Black horsemen in 19th-century American art.

Jess is an Australian zoologist and osteologist managing a prep lab at the Smithsonian. Fascinated by skeletal structures since she preserved her own dog's bones at age seven, she approaches her work with meticulous attention to detail. Her assignment to locate and evaluate an old horse skeleton in a museum attic draws her into an unexpected historical investigation.

Thomas is a former veterinary student who supports himself by painting equine portraits for wealthy Southern gentlemen. He also works as a racing reporter for turf publications. Though he privately opposes slavery, he conceals his political views to maintain his access to elite racing circles and lucrative commissions.

Martha is a successful Manhattan gallerist specializing in modern art. She grew up in a wealthy equestrian family but distanced herself from the sport following a fatal riding accident involving her mother. She relies on her sharp eye for artistic talent to build a respected gallery independent of her father's influence.

Lexington is a legendary bay Thoroughbred racehorse whose speed defines an era of American turf racing. Sired by the notoriously aggressive Boston, he develops a cooperative and highly intelligent temperament due to careful early socialization. His athletic career involves record-breaking triumphs, intense physical demands, and shifting ownership.

Harry is a highly respected free Black horse trainer working at The Meadows. Having purchased his own freedom, he saves his racing earnings to eventually secure emancipation for his son. He survives the dangerous social environment of the antebellum South by maintaining a cooperative, cautious demeanor with his wealthy employers.

Ten Broeck is a Northern racing promoter residing in Louisiana who operates the Metairie racetrack. He approaches horse racing purely as a lucrative business, prioritizing spectacle and gambling profits over the health and safety of the animals. He aggressively exploits the legal vulnerabilities of Black horsemen to acquire valuable horses.

Dr. Warfield is a retired obstetrician and wealthy gentleman farmer who owns The Meadows. He relies heavily on the expertise of Black horsemen to maintain his elite breeding operation. He treats his enslaved workers better than many of his peers but prioritizes his racing reputation above their security.

Mary Barr is the spirited granddaughter of Dr. Warfield and daughter of a vocal abolitionist. She shares a long-standing, quiet friendship with Jarret, who taught her to ride when she was young. She inherits her father's strong moral convictions and willingness to break societal rules.

Cassius is Dr. Warfield's wealthy son-in-law and a dedicated abolitionist who emancipated the enslaved people he inherited. His vocal opposition to slavery creates tension among the Kentucky racing elite and distances him from his extended family.

Catherine is an English equine veterinarian conducting a research project on the physiological durability of 19th-century racehorses. She brings crucial historical context to Jess's skeletal analysis, correctly identifying the anonymous bones in the Smithsonian as those of a legendary stallion.

Annie is Martha Jackson's housekeeper in 1950s New York. She is a hardworking woman from rural Ohio who quietly appreciates the modern art in Martha's gallery. She seeks to sell a 19th-century painting passed down through her family to help fund her brother's education.

Viley is a member of the Southern racing elite who initially collaborates with Ten Broeck. He leverages the racist bylaws of the Kentucky Association to separate Harry Lewis from his horse.

Julien is a refined portrait painter born to an English father and a Black mother. Having studied in Paris, he possesses significant artistic mastery and becomes a crucial mentor to Thomas J. Scott.

Robert Alexander is a prominent horse breeder in Kentucky who acquires Lexington to serve as a stud. He recognizes Jarret's vast knowledge of Thoroughbred pedigrees, promoting him to primary record keeper and barn manager.

Cyrena is Martha Jackson's mother and a fiercely ambitious equestrian competitor. Her tragic death during a riding accident permanently alters her family's relationship with the horse world.

Howard is Martha Jackson's wealthy father. He spares no expense to support his wife's competitive riding career but abruptly sells their horses following her fatal accident.

Clancy is Theo's loyal rescue dog. He accompanies Theo on his runs and provides quiet companionship in his Georgetown apartment.

Daniel is Theo's college friend. He serves as a sounding board for Theo's thoughts on his new relationship and shares his hyper-vigilance regarding racial dynamics in America.

Beth is an enslaved woman at The Meadows who begins a relationship with Harry Lewis. Harry ultimately uses the money he had saved for his son's freedom to secure her emancipation.

May is an enslaved woman who moves in with Jarret after her husband is sold to a plantation in Louisiana. She shares a warm, practical companionship with Jarret while raising her young son.

Robert is May's husband who was sold away from Kentucky. He volunteers for service in the Union Army to secure his freedom and eventually returns to retrieve his family.

Jackson Pollock is a famous abstract expressionist painter and a friend of Martha Jackson. He exhibits needy and manipulative behavior, though Martha respects his artistic talent and helps boost his notoriety.

Lior is Theo's editor at Smithsonian magazine. He directs Theo to the American Art Museum's storage center, inadvertently launching Theo's deeper investigation into equestrian art.

The widow is Theo's elderly neighbor who dismisses his polite attempts at conversation. She places a valuable equestrian painting in a discard pile following her husband's death.

Horace Wallis works in the Smithsonian's Affiliates division. He contacts Jess when his team loses track of a 19th-century horse skeleton requested by a visiting researcher.

Jeremy Raines is an art conservator at the Museum Support Center. He uncovers the signature of Thomas J. Scott beneath the grime on Theo's painting, confirming its historical origins.

Paul Mellon is a billionaire owner of fine racehorses. Martha approaches him hoping he will purchase her newly acquired 19th-century portrait of Lexington.

Lee Krasner is Jackson Pollock's wife and a fellow aspiring artist. She remains ready to assist her husband during his volatile creative episodes.

Colonel Bruce is an editor at the turf racing publication. He holds possession of Thomas J. Scott's finest painting of Lexington during the post-war era.

Gil Patrick is a highly experienced jockey known for his patient and honorable treatment of his mounts. He quickly identifies Lexington's physical limitations and collaborates with Jarret to protect the horse.

Justine Treadwell is a reporter for The Washington Post who focuses on issues of human rights and police misconduct. She approaches Jess seeking information about a recent tragic event.