This map presents the terrestrial ecosystems in the conterminous United States, and was developed as part of the United States Geological Survey’s (USGS) effort to model the distribution of terrestrial ecosystems using the geospatial mapping methodology that was developed from a deductive, biophysical stratification approach to delineate ecosystems by their major structural elements (Sayre and others, 2009). Each major structural component of ecosystems (land surface forms, surficial lithology, bioclimates, topographic moisture potential, and so forth) was modeled and then spatially combined to produce a new map of biophysical settings, termed ecosystem structural footprints. These ecosystem structure units characterize the abiotic (physical) potential of the environment. As the final step in this process, the unique structural footprints are aggregated into the terrestrial ecosystems classification that was developed by NatureServe (Comer and others, 2003). Additional information and access to this data is available at http://rmgsc.cr.usgs.gov/ecosystems/.