General areas of geothermal occurrences and resource types
in the United States.
From Energy and Geoscience Institute, University of Utah.

Most of the known hydrothermal resources and all of the presently known sites that are capable of electric power generation are in the western half of the U.S. (including Alaska and Hawaii).

The majority of thermal springs and other surface manifestations of underlying geothermal resources are also in the west.

Large areas underlain by warm waters in sedimentary rocks exist in Montana, North and South Dakota and Wyoming (Madison Group aquifers), but the extent and potential of these resources is poorly understood.

Another important large area, much of which is underlain by low-temperature resources, is the north, northeast-trending Balcones-Ouachita structural belt in central Texas.

The geopressured resource areas of the Gulf Coast and surrounding states are also shown.

Resource areas indicated in the eastern states are speculative because little drilling has taken place to confirm their existence.

Low- and intermediate-temperature resources are much more plentiful than high-temperature resources. There are many thermal springs and wells that have water at temperatures only slightly above mean annual air temperature, which is the temperature of most non-geothermal shallow ground water.