This file contains 15 net sand isopach grids that represent the summed true vertical thickness (TVT) of sand intervals between 15 stratigraphically adjacent horizons picked on borehole geophysical logs in the Southwestern Wyoming Province. In wells where adjacent horizons are missing, no TVT value is calculated. The TVT values are a measure of vertical thickness and do not account for the structural dip of units encountered in the wellbore. The 15 stratigraphic horizons are the tops of 15 regional flooding surfaces F1-15. Net Sand was determined by normalizing gamma ray logs and using a cut-off of 85 API units and then summing each interval. For more detailed stratigraphic information, please see the associated USGS SIM file XXXX, data table, and type log image. This file is a child item of a larger data release titled "Digital Stratigraphic and Structural Grids of the Lewis Shale in the Eastern Part of the Southwestern Wyoming Province, Wyoming and Colorado".