Here's why:
* Appearance: The horse in the film, ridden by Clint Eastwood's character "Manco," has the characteristic build and coat of a Morgan horse: sturdy, muscular, with a short, thick mane and tail, and a distinctive "foxiness" around the eyes.
* Popularity in Westerns: Morgan horses were popular choices for Westerns during the 1960s, due to their versatility, strength, and reliable temperament.
However, it's also possible the horse was a mix of breeds. The film's director, Sergio Leone, often utilized a range of horses for his Westerns, sometimes using local breeds available in Spain, where filming took place.
Ultimately, the specific breed remains a subject of speculation. However, the most likely contender based on its appearance and the common practice of using Morgans in Westerns is a Morgan horse.