A friend of mine claims that ancient Norse runes were once found in the state Minnesota and have been verified to be true. His source: "it was all over the news ten years ago." I have read that the Kensington runestone is widely regarded by scholars to be a hoax. Is there any evidence of Viking leaving runes or any other artifacts in Minnesota? And what do historians think of the Kensington runestone?
No, the only really agreed-upon site would be L'Anse aux Meadows in Newfoundland. There are some other finds and sites in places like Maine and Baffin Island, some of questionable authetnicity, but even then that's far from Minnesota. It'd be rather remarkable coincidence for them to make their way 1000 miles inland (for non-obvious reasons) to the specific place where Scandinavians would settle 1000 years later.
The Kensington runestone has never been regarded by experts as anything but a hoax from the start. Even if you ignore the strangeness of where it was found (and when and by whom and so on), it's just wrong in every way it could be. It invents some its own runes that didn't exist, uses words that didn't exist at that time ('opdagelsefärd'), is written in essentially modern Swedish, with what'd be completely wrong grammar for that time.
I mean it's so very anachronistic, it was written using more modern Swedish than used formally at that time, in 1898! Scandinavian (and English) verbs used to be declined by person (like "I am", "you are", etc) and number ("I was", "We were"), by 1900 declension by person had been dropped but it was still common in Swedish to use plural verb forms, especially in formal writing. English is in a bit of a similar situation now, where some people say "we was" rather than "we were" but in formal contexts still use the latter. ("analogical levelling" is the linguistics term for this kind of thing)
Well anyway, the Kensington stone doesn't use plural verbs; it says "vi var" (~"we was") and not "vi voro" (we were). (it also uses "vi kom" and "vi hade", also wrong) Writing "vi var" was acceptable Swedish (or Norwegian) in 1900 but already wrong by 1800. Go to the 14th century and it's even more wrong, as it should be "vir varom" (with spelling variants like wir but not vi; dropping the '-r' at the end came later), because now it's a different set of endings because the words were inflected by person as well as number. The same goes for the other verbs. On top of that there are missing case inflections and stuff, but I think you get the point. It's not just a hoax but a quite unsophisticated one.