The Leif Erikson one is very subjective though; you could celebrate:

• The first humans to cross the Bering Strait, which is a long extinct lineage
• The earliest ancestors to settle the Americas, whom we don't even know the descendants of
• The first Europeans to reach the Americas, ie Leif Erikson (Polynesia did it much later)
• The first people to cross an ocean to get to the Americas, most likely Polynesians but possibly Columbus
• The first Europeans to form a permanent settlement in the Americas, ie Columbus
• The founders of the forerunner to the US, ie Walter Raleigh & co
• The founding fathers for founding the US

And plenty more I'm sure you could come up with

Climate change was universally agreed upon to exist and be caused by people 30 years ago.

It certainly wasn't