The most widely accepted theory traces the ancestry of Banker Horses to Spanish horses introduced during the 1500s and early 1600s. Explorers, colonists, and maritime expeditions transported horses throughout the New World, establishing populations in regions that were previously without them. Some of these animals eventually became separated from direct human control.

For generations, local legends suggested that shipwrecks contributed to the establishment of the horse population. According to these stories, horses survived maritime disasters and reached nearby islands, where they later reproduced. While the shipwreck explanation remains popular, modern research suggests that intentional introduction may have played a larger role than previously believed.

Historical records indicate that Spanish colonial horses were widely distributed throughout portions of the southeastern United States. As settlements expanded and transportation routes developed, horses became increasingly important for travel, labor, and communication. Some populations eventually became feral and adapted to life outside human management.

Genetic studies have provided additional support for Spanish ancestry. Researchers have identified characteristics linking Banker Horses to colonial Spanish horse lineages. These findings help explain why the population differs from many modern domestic breeds.

The early history of the Banker Horse resembles a historical puzzle assembled from archaeology, genetics, written records, and local tradition. While some details remain uncertain, evidence consistently points toward a deep connection with the earliest European horse populations introduced to North America.