Paleomagnetic projects in California, Nevada, and Arizona include many examples where Applied Paleomagnetics provided paleomagnetic services to petroleum and geotechnical companies since 1986. Our paleomagnetic projects in California include extensive use of our paleomagnetic core orientation service to determine natural fracture, bedding, and in situ stress orientations in the San Joaquin and Santa Maria basins and in the Santa Barbara Channel in the following oil fields: Lost Hills, Midway-Sunset, Kern River, Railroad Gap, Leroy, South Ellwood. We paleomagnetically oriented fractures and bedding in cores from the following formations in southern California: Vaqueros, Topanga, Monterey, Puente (La Vida member), Capistrano, Tulare, and we paleomagnetically oriented natural fractures in deep subsurface cores from the Medicine Lake geothermal field in northern California. Also in California we conducted paleomagnetic fault studies on the San Andreas Fault at Pallett Creek, the F-1 and Foothills Fault System near the Auburn dam site, and faults near the Humboldt nuclear reactor. Our paleomagnetic projects in California include magnetostratigraphic studies of the Monterey, Tulare, and Saugus formations, and of Precambrian-Cambrian boundary strata in the Inyo Mountains and Nopah Range. Our paleomagnetic projects in Nevada focused on magnetostratigraphic and tectonic rotation studies in the Desert Range near the Las Vegas Valley Shear Zone. Other paleomagnetic projects we conducted in California and Nevada include measuring magnetic susceptibility and other magnetic properties at the Geysers geothermal field in northern California; measuring magnetic changes associated with dolomitization and hydrocarbons in the Monterey Formation and with landslides in the Capistrano Formation; and measuring magnetic susceptibility of cores from Railroad Valley, California, and from Lake Mead, Nevada. We used paleomagnetic techniques to detect vertical-axis tectonic rotations along the San Andreas Fault at Lost Hills and Pallett Creek and in Monterey cores from the Santa Maria Basin and Santa Barbara Channel. In southwest Arizona, we provided paleomagnetic constraints on timing of detachment faulting. Other paleomagnetic projects we conducted in California and Nevada focused on paleomagnetic dating of authigenic magnetite, hematite, and pyrrhotite that grew during regional or local fluid-migration events. In northern California, we paleomagnetically dated authigenic magnetite in fault gouge at the Auburn dam site; in SE California and southern Nevada, we paleomagnetically dated magnetic minerals formed during late Paleozoic compression and late Cenozoic extension; and in SW California, we paleomagnetically dated magnetic minerals associated with fluids driven by uplift of the Transverse Ranges in cores from the Monterey Formation. In Orange County, we paleomagnetically oriented fractures and bedding in cores from the Frank R. Bowerman and Prima Deschecha landfills to minimize risk associated with landslides at proposed excavations.