Through extensive crossbreeding with local mares, these stallions spread the Clydesdale type throughout the areas where they were placed, and by 1840, Scottish draught horses and the Clydesdale were one and the same. In 1877, the Clydesdale Horse Society of Scotland was formed, followed in 1879 by the American Clydesdale Association (later renamed the Clydesdale Breeders of the USA), which served both U.S. and Canadian breed enthusiasts. The first American stud book was published in 1882. In 1883, the short-lived Select Clydesdale Horse Society was founded to compete with the Clydesdale Horse Society. It was started by two breeders dedicated to improving the breed, who also were responsible in large part for the introduction of Shire blood into the Clydesdale.