The Mandan and Hidatsa of the Dakotas had trade routes to the west coast, desert Southwest, and much farther east. Their principal outgoing trade item was Knife River flint. Ultimately, they had descendants of Spanish horses from Texas and New Mexico not long before the fur trade began. The earliest evidence of Sioux use of the horse dates to a winter count robe that shows a horse image representing 1708.
Many people today just don't understand that despite not having horses for much of their early history, trade was COMMON all over the western hemisphere. And it was big business. People weren't born and then staked to the ground with a short rope, for pete's sake. Europeans didn't exactly invent itchy feet. From first settle people to arrive in what is now Alaska to arriving in southernmost South America may have happened in as little as 800 years.
Nope, trade is not shocking. What it IS is VERY INTERESTING!