Compiles over 1,500 ground-based facility measurements to develop a high-resolution, measurement-based inventory of 2021 U.S. oil and gas methane emissions. Total methane emissions are estimated to be roughly twice the U.S. EPA Greenhouse Gas Inventory, corresponding to a 2.6% gas-production-normalized methane loss rate, consistent with satellite data. Emissions vary widely by basin, with oil-dominant regions like the Permian, Bakken, and Uinta showing much higher loss rates than gas-dominant regions such as the Appalachian and Haynesville. Comparisons with airborne MethaneAIR data show good agreement with regional estimates and indicate that diffuse sources account for most emissions in key basins.