We have developed a spatial database of historic natural fire regimes for the eleven western States to provide information in support of expected national increases in prescribed burning. Fire regimes are described in terms both of frequency and severity, and we have classified five distinct fire regimes: <35 years/non-lethal (mostly forested land); <35 years/stand replacement (grasslands and shrublands); 35-100+ years/mixed severity; 35-100+ years/stand replacement; 200+ years/stand replacement. The base-layer spatial data we used was a 159-class Land Cover Characterization database derived from seasonal NDVI profiles by USGS EROS Data Center. To assign fire regimes to the Land Cover Characterization database, we integrated four additional sources of biophysical data, including a 500 meter digital elevation model, Kuchler's Potential Natural Vegetation, 4th-Code hydrologic units, and ecological subregions (Bailey's sections). The resulting knowledge will help decision-makers determine what level of fire activity may be required. For example, can initial entry fire be used for maintenance; can fire be used to achieve restoration objectives, or is supplemental mechanical treatment required as a precursor to prescribed fire?