List of ecoregions in the United States (EPA)

The Commission's 1997 report, Ecological Regions of North America, provides a framework that may be used by government agencies, non-governmental organizations, and academic researchers as a basis for risk analysis, resource management, and environmental study of the continent's ecosystems.

Ecoregions may be identified by similarities in geology, physiography, vegetation, climate, soils, land use, wildlife distributions, and hydrology.

Level I divides North America into 15 broad ecoregions; of these, 12 lie partly or wholly within the United States.

[2] Level III subdivides the continent into 182 smaller ecoregions; of these, 104 lie partly or wholly with the United States.

The classification system excludes the U.S. state of Hawaii, which is not part of the North American continent.