US GAP Land Cover for the US
The USGS Gap Analysis Program (GAP) Land Cover Data Set includes detailed vegetation and land use patterns for the continental United States. The data set incorporates the Ecological System classification system developed by NatureServe to represent natural and semi-natural land cover. The 590 land use classes in the data set can be displayed at three levels of detail, from general (8 classes) to most detailed. The Land Cover Data Set can be used to identify those places in the country with sufficient good quality habitat to support wildlife, a key step in developing sound conservation plans.
The data are available to download; http://gapanalysis.usgs.gov/gaplandcover/data/download/
or to view on the web: http://dingo.gapanalysisprogram.com/landcoverv2/Map.aspx