The Boulder Timeline was made possible with underwriting support from WK Real Estate, Boulder.
300 MILLION YEARS AGO
The Fountain Formation was deposited in a series of alluvial fans. This geologic unit includes the Flatirons, Boulder’s iconic red mountain backdrop.
68 TO 10 MILLION YEARS AGO
The Front Range rose, eroded and rose again.
15,000 YEARS AGO
Ice Age glaciation and continuing stream erosion began to give the high peaks and the foothills the shapes they have today.
For thousands of years, the Boulder Valley was home to several tribes of Native Americans.
1600-1800s European colonization forced many Native American tribes further west. The Arapaho and Cheyenne, for example, moved from the Great Lakes Region to the Plains. The nomadic Southern Arapaho, led by Chief Niwot, often wintered in Boulder Valley.