When did horses arrive in America?
"when the Spanish arrived, soon after America was discovered by Christopher Columbus."
I left the previous answer in tact as a learning moment. Can you believe that people still couch what Columbus did in this way? "Discovered"
The horse actually originated in the Americas long before humans but was gone by the time the first humans arrived. The horse was re-introduced by the Spanish as they began to explore and exploit the "New World." So - right around 1500.