A PhD candidate in Art History at Georgetown University, Theo is of mixed heritage, with parents who served in the foreign service. Raised in various countries, Theo grows into a star polo player but quits due to racism. He transitions to art history, focusing on Black horsemen in 19th-century equine paintings. He becomes intrigued by Lexington’s legacy and investigates it further.

An Australian zoologist skilled in skeletal articulation, Jess is a key figure in *Horse*, taking on the task of rearticulating Lexington’s skeleton at the Smithsonian. Her work helps elevate Lexington’s legacy. She shares a complex relationship with Theo, sparked by their shared interest in Lexington, and grapples with her own prejudices and perceptions.

A portrait artist originally aspiring to be a veterinarian, Scott becomes known for painting horses and works in Kentucky during Lexington’s time. Befriending Jarret, he paints several influential works of Lexington and Jarret, contributing to Lexington's legacy. Scott's portraits become significant pieces of equine art history.

A successful New York art gallery owner from a wealthy horse-loving family, Martha discovers a painting of Lexington which she eventually donates to the Smithsonian. Though she initially underestimates her housekeeper’s cultural knowledge, her estate contributes significantly to preserving Lexington's legacy.