How long ago did the Europeans "stumble" upon the Americas?

Question

How long ago did the Europeans "stumble" upon the Americas?

Answer 1

I believe it was the year 1492, because of the song

"In 1492, Columbus sailed the ocean blue"

Answer 2

Nobody knows for certain, but the best evidence suggests about 1000 AD.  Chinese explorers might have reached the west coast as early as the 7th century.

Answer 3

There are hints that European fisherman may have stepped ashore as early as the 10th Century.  They fished close to New England and Canada's maritime colonies, and it's reasonable to suspect that they stopped for water, wood, etc.  The Vikings arrived in the 12th, and there are signs that others including the Celts paid visits.