Time of earliest humans in the North America?

Question

How far back is it noted that there were humans living in the lands that are now North America?

Answer 1

The Discovery channel had a special about the Ice-Age Columbus. They suggested 50,000 years ago on the East Coast. The others didn't cross the Bering Straits until about 15,000 years ago.

This isn't the entire answer. Every once in a while they come up with a skeleton older than both dates.

Answer 2

New evidence has come to light, published in a book called "1491," that suggests people on North America may pre-date the so-called "Old World."