This digital dataset was created as part of a U.S. Geological Survey study, done in cooperation with the Sonoma County Water Agency and the City of Petaluma, to be used as the digital hydrogeologic input data for numerical simulation of the groundwater system of the Petaluma Valley Watershed, Sonoma County, California. Elevation, thickness, and extent of the hydrostratigraphic units define the geohydrologic layering of the digital framework model. The location of faults may be used to define the location of potential horizontal flow barriers in numerical simulation of the groundwater system. The intended uses of this dataset include, but are not limited to, natural resource modeling, mapping, and visualization applications. This digital dataset represents the three-dimensional hydrogeologic framework for the Petaluma Valley Watershed, Sonoma County, California. The data define the elevation, thickness, and extent of the principal hydrostratigraphic units of the region, and faults that cut these units. The digital data describe the following eight hydrostratigraphic units: Qal, Quaternary alluvial deposits; BM, Holocene Bay Mud deposits; Qmix, Quaternary mixed unit; WG, Wilson Grove Formation; PF, Petaluma Formation; SV, Sonoma Volcanics; TV, Tolay Volcanics; BSMT, Basement rocks. Most of the three-dimensional hydrogeologic framework data are contained within a single polygon feature class (HFM_300m_polys), which contains a mesh of polygons that represent model cells that have multiple attributes including X, Y, elevation, and thickness of each hydrostratigraphic unit. Faults are provided as a separate line features class (HFM_faults). Two additional ascii files contain the model output from 3D geologic framework and lithologic properties models for the Petaluma groundwater basin. An additional tabular data file contains specific capacity data calculated from well pumping tests.