Since Columbus Day was federally recognized in 1937, much has been learned about what really surrounded Christopher Columbus' journeys to the "New World". A growing number of historians believe Columbus was more of a business man than an explorer, that enslaved and killed the natives he encountered in his search for riches. Even not taking Columbus' character into consideration, it has also been established that there were others before him that were lost to popular history.
To avoid claims of another named explorer for the day, such as "Leif Ericson", renaming it "Discovery Day" or "Exploration Day" would be more appropriate.
It could also be a celebration of so much more than what one person did to supposedly discover what was already discovered by its inhabitants.