Surficial geologic map of the eastern Snake River Plain and adjacent areas, 111° -115° W., Idaho and Wyoming

This map portrays the distribution of surficial materials that cover most of the landscape of the eastern Snake River Plain and adjoining areas in a larger part of southeastern Idaho and a very small area in western Wyoming (fig. 1). Almost 350,000 people or 40 percent of Idaho's (estimating 1979 population from Rand McNally (1979)) live in the area, which constitutes about 30 percent of Idaho's land area.

The great majority of this population resides in the major irrigated agricultural areas along the Snake River between American Falls and Ashton and between Bliss and Lake Walcott, which contain the important and growing commercial centers of Rexberg, Idaho Falls, Blackfoot, Pocatello, Burley-Rupert, Twin Falls, and Jerome. These areas encompass almost two-thirds of Idaho's irrigated croplands, and, along with water, are the region's most important resource. Major products include potatoes, sugar beets, alfalfa, small grains, and other crops.

Along the margins of the Plain and in adjacent basins, smaller areas of irrigated farming and population are present, such as Teton Basin, Mud Lake area, Big and Little Lost River Valleys, Big and Little Wood River Valleys, and Raft River Valley. In several of these basins and in nearby upland areas, dry farming of grains is important. Some of these lands are now being converted to irrigated croplands. Grazing is the dominant economic use of grasslands on the Plain in adjacent basins and uplands. At present, industry assumes a minor role in the region's economy, although food processing and nuclear research at the Idaho National Engineering Laboratory (INEL) locally or important.