Although bat diversity across much of California has been relatively well studied, the Sacramento Valley remains a poorly documented region due to its extensive agricultural transformation and historical oversight during early 20th-century surveys. To address this knowledge gap, we synthesized museum specimen records of bats collected in the Sacramento Valley from 1885 to 2025. Specimen data were compiled from 26 natural history collections through online databases (VertNet, ARCTOS, and UC Davis DIGICORE), filtered by location and georeferenced to determine seasonal and spatial patterns of bat occurrence. We identified 691 specimens representing 14 bat species from 11 counties in the region. These data revealed distinct seasonal patterns of occurrence and sex-specific distributions for several species, including Eptesicus fuscus, Lasionycteris noctivagans, Lasiurus cinereus, and Lasiurus frantzii. Our findings demonstrate that historic specimen records can provide important insights into demography and seasonal movements of bats in regions where long-term acoustic or capture-based studies are limited. This synthesis not only establishes a critical historical baseline for bat distribution in the Sacramento Valley but also highlights the continued relevance of museum collections in contemporary ecological and conservation research.