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Time line of the geologic history of the United States - 10th millennium BC - 9th millennium BC

The 10th millennium BC in North American history provides a time line of events occurring within the present political boundaries of United States (including territories) from 12,000 years ago through 9001 BC in the Gregorian calendar. Although this time line segment may include some European or other world events that profoundly influenced later American life, it focuses on developments within Native American (and Polynesian) communities. Because the indigenous peoples of these regions lacked a written language, we must glean events from the admittedly very incomplete archaeological record and place them in time through radiocarbon dating techniques.

Because of the inaccuracies inherent in radiocarbon dating and in interpreting other elements of the archaeological record, most dates in this time line represent approximations that may vary a century or more from source to source. The assumptions implicit in archaeological dating methods also may yield a general bias in the dating in this time line.

• 9500 BC: Cordilleran and Laurentide ice sheets retreat enough to open a habitable ice-free corridor through Canada along the eastern flank of the Rocky Mountains.

• 9500 BC: People craft early Clovis spear points, knives, and skin scrapers from rock in New Mexico.

• 9500 BC: Clovis-like materials spread from the Great Plains and American Southwest toward the Atlantic seaboard.

• 9001 BC: Archaeological materials found on Channel Islands off the California coast and in coastal Peru.

• 9001 BC: Human settlers arrive in the Great Basin with its cool, wet prevailing climate.