Not much, since Columbus (and after him the increasing flood of explorers from Europe) didn't get to the Americas until almost 1500.
There are a couple, though, but they are so far in the past that here are controversies about them:
http://www.google.com/search?hl=en&client=firefox-a&rls=org.mozilla:en-US:official&hs=Ssr&ei=E-liS4XpK4mQNo2u3KEO&sa=X&oi=spell&resnum=0&ct=result&cd=1&ved=0CAYQBSgA&q=leif+erikson&spell=1
http://archaeology.about.com/od/bcthroughbl/qt/beringia.htm
What was the human hisory between North American Asia Eurasia and Europe before the 1450's?
1 answer