Indigenous Peoples' Day (& Columbus)
The dumbass mariner you celebrate wasn't even right about the size of the Earth. Columbus was wrong by the science and mathematics of the age, not just by modern science. That's a hell of an albatross around your holiday's neck.
https://en.wikipedia.org/wiki/Voyages_of_Christopher_Columbus#Diameter_of_Earth_and_travel_distance_estimates
Indigenous Peoples' Day (& Columbus)
No one thought the Earth was flat. The literate knew it's round & how big around (except for some conspiracy theorists relying on obvious unit conversion errors), and the uneducated never traveled far enough to know or care.