As late as 1700, most North American tribes lived without horses. The horse arrived in the New World with the Spanish in the 1500s. It was a humongous military advantage over the people the Spanish wished to conquer and colonize. Eventually, however, some horses escaped and started living and multiplying in the wild. It was then, in the first decades of the 1700s, that horses almost totally transformed the culture of the plains and the southwest.