Hunter-camped sites above 10,000 feet, evidenced by fire hearths, stone tool debris, and animal bones, have been dated to several thousand years before the present.

The pattern that emerges from this evidence is of a Rocky Mountain high country that was not marginal or rarely used but that was actively integrated into the seasonal subsistence rounds of prehistoric communities.

This integration makes ecological sense.

The alpine and subalpine zones of the Rockies contain specific resources not easily accessible at lower elevations — particularly the large game animals that use high country in summer, moving above treeline to escape insects and heat and to access the nutritious alpine vegetation.

Bison, bighorn sheep, deer, elk, and pronghorn all use high-altitude terrain seasonally, and people who could access that terrain could hunt them there in ways that were not possible at lower elevations where the same animals would be in different behavioral modes.