I find things like this interesting.

Columbus was certainly not the first European to discover North America.

I've heard of this, but I haven't been there.

While reports of Scandinavian people visiting North America before Columbus seem plausible to me, especially in places like Greenland (that's considered North America, right?), Canada, and the Northeastern US, it seems less likely that they would have made it all the way to Oklahoma.

But our theories about the past are disproven all the time, it certainly is possible that they traveled that far into the interior, or perhaps that the writing system did.