Earliest archaeological evidence of Native American Hunter-Gatherers in the mountains and valleys of North Central Colorado dates to a rare but growing presence of Clovis (13,200-12,800 cal yr bp) and Folsom (12,800-12,160 cal yr bp) hunter-gatherers in Terminal Pleistocene and earliest Early Holocene times. By ca. 10,900 cal yr bp, significantly warmer Early Holocene climate led to development of annual seasonal transhumant migrations of Late Paleoindian hunters and game animals to the region’s high tundra and construction of built game drives, a Native American subsistence pattern which persisted through early historic times. Two decades of high altitude archaeological and paleoenvironmental research by the authors provided substantive documentation of cultural contexts and chronologies of that transitional period through large-scale survey, excavations, and dozens high and low elevation lake and fen sediment core studies.