A methodology has been developed at the U.S. Geological Survey (USGS) for making earthquake catalogs for seismic hazard analysis. A new catalog is assembled from several preexisting catalogs. Uniform moment magnitudes and related parameters for estimating unbiased seismicity rates are calculated. Duplicates, explosions, mining-related earthquakes, and induced earthquakes are flagged, and the catalog is declustered. Distinct catalogs are made for the central and eastern U.S. and the western U.S. This data set is the earthquake catalog without duplicates for the western U.S., for use inside the UCERF3 zone (Catalog A).