California is considered a biodiversity hotspot based on its high species richness and endemism, and the threats to ecosystems that support these species. Small mammals are key components of healthy ecosystems, serving as seed and fungal dispersers, prey, and habitat engineers. Recently, Sierra Nevada ecosystems have experienced an increasing amount of change, including climate change, more severe and frequent fires, and associated vegetation change. Small mammals are demonstrably sensitive to changes in climate and habitat, but the long-term influence of fire on small mammal communities is poorly understood. We aim to explore the drivers of small mammal richness, focusing on fire, habitat, and climate. Historical survey and resurvey projects provide high-quality species occurrence data from the last century in the Sierra Nevada. Results indicate that historic fire regime plays a key role explaining variation in modern small mammal richness across the Sierra Nevada and that inclusion of variables related to fire improves model fit compared to models with just climate and habitat. Overall, our work contributes knowledge on the factors influencing small mammal communities in an era of global change.