Are horses invasive to the U.S?`?

Question

I have heard alot of theories saying that horses are not native. Some say European explorers brought them in while others say that they came from south america. Some people believe that they have always been in the U.S. What is the real answer? please give sources!!!

Answer 1

The North Amerian continent used to have naturally occurring horses some thousands of years ago, but there was a bout of extinction of many large, native animals.  Those horses died out.  That left both American continents as horse-free zones until the Spanish turned up.