Detrital zircon U-Pb provenance and stable isotopic studies of three Paleogene southern Sierra Nevada (California) basins place new constraints on the paleoelevation history of the region. Age spectra from the Paleocene Witnet Formation within the southernmost Sierra Nevada link these sediments to source terranes that were at or near sea level in the early Cenozoic, while age spectra from the Paleocene Goler Formation, east of the Sierra Nevada, demonstrate isolation of southern Sierra Nevada basins from the continental interior and tapping of Jurassic and Triassic arc flank sources during the Paleocene. West of the Sierra Nevada, strata of the Eocene Tejon Formation are dominated by Cretaceous zircons sourced from the Sierran batholith. Goler Formation carbonate δ18O suggests Paleocene paleoelevations of 1–2 km for the central and southern Sierra Nevada. Taken together, these data indicate a Paleogene southern Sierra Nevada with modest elevations, locally dissected to sea level by rift basins formed by Late Cretaceous lithospheric collapse. These results place new limits on the amount of regional middle to late Cenozoic elevation gain that may have resulted from the loss of dense, mantle lithosphere from below the central and southern Sierra Nevada, and point to possible north-south variations in the topographic evolution of the Sierra Nevada.