50,000 years ago, that is.
It's one thing to read about impact craters; it's something altogether different to visit one. Barringer Crater, near Flagstaff, Arizona, is a short 6 mile drive from Interstate 40 and is supposed to be the best preserved impact crater on earth out of the 128 discovered so far.
I recommend a visit if you are so inclined. With the crater itself and the revamped visitor center, the visit takes about 1-2 hours. I visited Barringer crater for the seconds time this year. Read more about the crater here: Barringer Crater.