This volume identifies, characterizes, and quantifies United States coal resources that are of possible interest for underground coal gasification (UCG). The material presented can be used as a starting point for identifying candidate site areas, but it is not sufficiently detailed to be useful in the selection of specific sites. Section 1.0, the introduction, discusses geological and other factors affecting UCG site selection. It also explains why coal rank, seam thickness, and seam depth were selected as the preliminary screening criteria used to define UCG resources. Section 2.0 discusses eastern United States coal resources for UCG, and Section 3.0 discusses western states resources. Each state's resources that meet the preliminary screening criteria are discussed, with available tonnage estimates, chemical analyses, and information on depth, location, and thickness being included. Other data of possible use in evaluating resource suitability for UCG are also provided, and a subjective evaluation of each resource's potential suitability is made.