The state and federally endangered salt marsh harvest mouse (SMHM) was first described 115 years ago, and despite having a relatively restricted and delineated range (San Francisco Estuary) a comprehensive "census" of the species had never been attempted. In 2019 a group of researchers applied successfully to the National Fish and Wildlife Foundation for funding to plan and implement the first ever Rangewide Survey for SMHM. The planning process was supported by both an analysis of potential habitat value throughout the Estuary based on historical trapping data, and the recent development of methods for assessing occupancy via fecal DNA. Sampling areas were selected systematically across the species range, and location and scheduling balanced staff availability, safety and accessibility, king tides, and other considerations. In all, 60 sites were selected for live trapping and 25 for fecal DNA sampling. Over 60 biologists and volunteers working across 9,000 trap nights processed 1,930 rodent captures, resulting in 651 individual SMHM captured at all but seven of the live-trapping sites. SMHM were also detected at 14 of the fecal DNA sampling locations. These results will inform ongoing analyses, and guide future conservation decisions and habitat management efforts, in support of SMHM recovery.