2014. National Atlas of the United States. This polygon shapefile consists of National Wilderness Preservation System areas of 320 acres or more, in the United States, Puerto Rico, and the U... National Atlas of the United States.
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2004. United States. Forest Service. This polygon shapefile is commonly called Bailey's ecoregions and shows ecosystems of regional extent in the United States, Puerto Rico, and the U.... National Atlas of the United States.
1966. Patuxent Wildlife Research Center. This line shapefile portrays the current routes used for conducting Breeding Bird Surveys in the lower 48 States. This layer is part of the 1997-20... National Atlas of the United States.
1941. Lannoo, Michael J., Blackburn, Laura, and Nanjappa, Priya. This polygon shapefile portrays the distribution of 10 selected amphibians in the United States, based on historical literature and museum records ... National Atlas of the United States.
1972. National Atlas of the United States. This polygon shapefile contains National Wilderness Preservation System areas of 640 acres or more, in the United States, Puerto Rico, and the U.S.... National Atlas of the United States.
2003. United States. Environmental Protection Agency. This polygon shapefile shows Omernik's Level III ecoregions, derived from a 1:7,500,000 map created by J.M. Omernik in 1987 and from refinements of... National Atlas of the United States.
1990. United States. Agricultural Research Service. This polygon shapefile portrays the spread, by year, of the Africanized honey bee (AHB) in the United States, Puerto Rico, and the U.S. Virgin Isla... National Atlas of the United States.
