Apparently English settlers started this tradition in the 1620s in their new American colonies. As a boy, I recall also celebrating the 'Harvest festival', from which 'Thanksgiving' sprang. In any event, it's a great opportunity (like Christmas and other festivals) of wishing fellow humans well. I'm certainly up for that.
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.