Worldwide, about 50% of wetlands have been lost. In the San Francisco Bay Estuary (SFBE) less than 10% of historical tidal wetlands remain, and those comprise a fragmented mosaic of natural and anthropogenically altered wetlands. Globally, only 5 species of vertebrates, and only one mammal, the endangered salt marsh harvest mouse (SMHM, Reithrodontomys raviventris), are restricted to coastal wetlands. SMHM is a unique wetland-adapted rodent endemic to the marshes of the SFBE. Conventional conservation practices have favored a push toward tidal restoration as a recovery action for SMHM. However, tidal wetlands are vulnerable to sea level rise and tidal restoration is slow and costly. Understanding the value of alternative habitat types can improve conservation of SMHM. We investigated the relative value of historical tidal and anthropogenic diked wetlands for SMHM. We found that both support similarly sized populations and similar numbers of reproductive females, but diked wetlands had higher densities of juveniles. Habitat use is similar between wetland types, but smaller home ranges in diked wetlands may indicate greater habitat value. Finally, preferred food plants occur at high densities in diked wetlands. This study – the first of its kind – greatly improves our understanding of the habitat requirements of SMHM. Diked wetlands have high habitat value for SMHM, possibly superior to tidal habitat; this result triples the acreage of “good” SMHM habitat in the SFBE. It also illustrates the importance of understanding the value of anthropogenic habitats for conservation of endangered mammals as historical habitat patches dwindle.