came to the mainland with the arrival of Cortés in 1519. By 1525, Cortés had imported enough horses to create a nucleus of horse-breeding in Mexico. Horses arrived in South America beginning in 1531, and by 1538 there were horses in Florida. From these origins, horses spread throughout the Americas. By one estimate there were at least 10,000 free-roaming horses in Mexico by 1553. In 2010, the Colonial Spanish mustang was voted the official state horse of North Carolina. Modern horses Many gaited horse and stock horse breeds in the United States descend from Spanish horses, but only a few bloodlines are considered to be near-pure descendants of original Spanish stock. Though many are described as horse breeds, it can be debated they are separate breeds or multiple strains of a single large breed. The Livestock Conservancy lists them as one breed, but also calls them "a group of closely related breeds" Various bloodlines or groups of Colonial Spanish horses are registered a number of different Associations. While some bands of modern mustangs have evidence of ancestry from the original Spanish imports, genetic analysis indicates that many free-ranging horses in the Great Basin descend from later breeds of draft horse, cavalry mounts, and other saddle horses. Where they have been found to have descended from the original Spanish horses, the Bureau of Land Management (BLM) and other agencies attempt to preserve them. Blood typing, along with phenotype and historical documentation have been used to confirm significant Spanish ancestry of a few BLM managed herds. In 1985, the BLM awarded a grant to the University of California, Davis, to conduct a three-year study on mustang genetics, including the percentage of original Spanish blood. Ann T. Bowling and R. W. Touchberry did not find much evidence of Spanish genetics in the Great Basin horses tested, but follow up work by Gus Cothran, then of University of Kentucky, carried on the study and found Spanish markers in the Pryor Mountain and Cerbat herds outside the Great Basin, and Sulphur Springs herd within it, later confirming the findings for the Sulphur Springs herd through mtDNA sequencing analysis. Some breeders and horse associations have used blood typing results to prove or disprove horses being of Spanish ancestry, but some horses of Spanish phenotype may not carry the expected Iberian blood markers. Conversely, some horses that lack Spanish type, such as certain strains of the American