National Wetlands Inventory (NWI)
The National Wetlands Inventory (NWI) has been producing wetland maps and geospatial wetland data for the United States since the mid-1970s. The focus has been on two fronts: 1) map or digital database preparation and delivery to the public, and 2) projecting and reporting on national wetland trends using a probability-based sampling design. Maps and geospatial data developed by the NWI is available online and can be downloaded by HUC 8 Watershed Boundary or by State. The data is downloaded as a .zip file that contains the following layers: wetlands polygon data, wetlands project metadata (includes image dates and project information), wetlands historic map information, riparian polygon data, riparian project metadata (includes image dates and project information), historic wetlands, historic wetlands project metadata (includes image dates and project information), and USGS HUC 8 Watershed Boundary.
The link address is: http://www.fws.gov/wetlands/Data/Data-Download.html