Georges Bank is a very large shallow area in the North Atlantic, roughly the size of a New England state, that serves as a fishing ground and whaling area (these days for watching the whales, not harpooning them) for ports in New England, New York and Eastern Canada. Eighteen thousand years ago, sea levels were globally at a very low point (with vast quantities of the Earth's water busy being ice), and at that time George's Bank would have been a highland region on the very edge of the North American continent, extending via a lower ridge to eastern Massachusetts and Rhode Island, and separated by a low plain (covered in part by glaciers) to the rest of New England.
As sea levels began rising around twelve thousand years ago, George's bank became a narrower peninsula and eventually an island visible from the mainland. We know that people lived on this island because artifacts of early Native American groups have been dredged up here, along with the teeth of Pleistocene elephants and other items.
Eventually, the island would have been too far from the shore to see, although one might expect people living on the island or the mainland would have known about the other lands, and probably about the people on them, as there is good evidence that maritime activity was fairly intensive in this region. Indeed, it may well have been the existence of George's Bank that fueled the maritime activity that was apparently much more intensive between five and seven thousand years ago in this region.
Read the complete story from Greg Laden's Blog.