This map shows the physical materials at the surface of the United States. Its design distinguishes between nineteen types of land cover including developed lands, wetlands, forests, farmed lands, and barren regions. Several classes of land cover found only in Alaska are shown. The data used to illustrate land cover comes from many individual images delivered by the Landsat satellite. This data is particularly useful for observing changes to the land surface over time. Two additional features make the map more useful. Small "thumbnail" maps that indicate where to find each land cover type on the larger map are included. Photographs that exemplify each land cover class are also shown. All States, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands are mapped at the same scale.