The Wisconsinian was the last major advance of continental glaciers in North America. This glaciation is made of three glacial maximums (commonly called ice ages) separated by inter-glacial periods (such as the one we are living in). These ice ages are called (from oldest to youngest); Tahoe, Tenaya and Tioga. The Tahoe reached its maximum extent perhaps about 70,000 years ago while little is known about the Tenaya. The Tioga was the least severe and last of the Wisconsinan group and reached its greatest advance 20,000 years ago and ended about 10,000 years before present (it started 30,000 years ago).
Reference
Geology of National Parks: Fifth Edition, Ann G. Harris, Esther Tuttle, Sherwood D., Tuttle (Iowa, Kendall/Hunt Publishing; 1997) ISBN 0-7872-5353-7
Today glaciers are found only in the polar regions and in high mountainous areas, but in the past, they covered vast areas of the Earth’s surface, and shaped much of the landscape that we see today.
Glacial cycles are composed of both glacial periods, in which the climate cools and glaciers grow, and interglacial periods, in which a warming climate causes the ice bodies to recede.
During the Late Wisconsinanglacial stage, most of Canada and parts of the northern United States were covered by two massive ice sheets: the Cordilleran which lay to the west of the Rocky Mountains and the Laurentide to the east.
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