The San Juan basin is a significant physical and structural element in the southeastern part of the Colorado Plateau physiographic province. The San Juan basin is in New Mexico, Colorado, Arizona, and Utah and has an area of about 21,600 square miles. The basin is about 140 miles wide and about 200 miles long. In the 1980’s and 1990’s, the U.S. Geological Survey's Evolution of Sedimentary Basins—San Juan basin study produced several reports on aspects of the stratigraphy and sedimentology of the basin. A report of the stratigraphy, structure, and paleogeography of Pennsylvanian and Permian rocks included 18 plates of contoured elevation and thickness data for various units (Huffman and Condon, 1993). This digital dataset contains spatial datasets corresponding to selected contour maps from the Evolution of Sedimentary Basins—San Juan basin study. The data help define the elevation, thickness, and extent of principal stratigraphic units of the basin. The digital data describe the following stratigraphic units: the Molas Formation, the Rico Formation, the elevation of the top of Permian strata, and the estimated thickness of Permian and Pennsylvanian rocks. Digital data for each unit are contained in individual features classes within a geodatabase (also saved as individual shapefiles). Feature classes have a single attribute, either elevation or thickness, that represents the contoured value. Contoured values are given in feet, to maintain consistency with the original publication, and in meters.