Until recently, the Nation lacked a detailed, nationally consistent land-cover map and database. Land-cover maps show the physical nature of the land, including vegetation, soil, rock, and manmade structures. Data can come from either aerial photography or satellite images. These maps are used for hundreds of purposes, including assessing ecosystem status and health, modeling nutrient and pesticide runoff, seeing spatial patterns of biodiversity, land use planning, developing land management strategies, and more.

The Multi-Resolution Land Characteristics Consortium (MRLC) is a group of federal agencies who began collaborating in 1993, pooling resources to assemble satellite imagery for the lower 48 United States. They developed a comprehensive database called the National Land Cover Datasets (NLCD), mapping 21 types of land cover that seamlessly covers the U.S. Each of the 66 mapping zones can also be looked at independently using common tools and techniques.

U.S. Geological Survey (USGS), U.S. Environmental Protection Agency, National Oceanic and Atmospheric Administration, NASA, USDA Forest Service, USDA Natural Resources Conservation Service, National Agricultural Statistical Service, USDI Bureau of Land Management, USDI National Park Service, USDI Fish and Wildlife Service, LANDFIRE, State of Illinois, State of Kentucky, State of Maine.

The NLCD system uses the "Database" approach to land-cover mapping. Instead of mapping speci. c land-cover types such as natural vegetation, agriculture, and developed areas, USGS scientists developed a procedure that identifies all of the physical characteristics of each satellite pixel, which are tiny squares of the land surface that, when put together, make up the image. The characteristics include visible and near-infrared reflected light, land elevation, slope, aspect, soil moisture, percent canopy density, percent impervious surface, and others. With these characteristics stored in a spatial database, users can specify the particular map they need.

The NLCD data are used by Consortium partners for many environmental, land management, and modeling applications, such as evaluating patterns of landscape change and mitigation of future impacts to ecosystems. In addition, NLCD data are an invaluable national resource used in a large number of applications ranging from commercial sector (locating cell-phone towers), scientific activities (quantifying potential pollution removal), education (landscape visualization), and government organizations (emergency response).The NLCD website delivers a standard map showing all 21 datasets. Alternatively, users can specify which data sets and data set parameters they want. The LANDFIRE Program uses this feature to add tree species and canopy structure information to produce fire fuel maps.