Recent data pertaining to the uplift of the Provo and Bonneville shorelines of the late Pleistocene Lake Bonneville are evaluated in a reanalysis using a rigorous model of deformation of a plane earth comprising an elastic layer overlying a viscoelastic channel. The new observations constrain the wavelength and amplitude of the uplift of two shorelines formed at two different epochs, and they partly resolve the ambiguities in the plausible mechanical parameters found in previous solutions. The results indicate that the effective thickness of the elastic lithosphere is 28 to 30 km, equal to the seismically determined crustal thickness in the region. The estimate of the upper mantle viscosity in the region varies from (1.5–3.4) ×lO19 Pa s to (2.1–5.8)×l018 Pa s, depending on whether the upper mantle is assumed to be of uniform viscosity or the flow is confined to a narrow channel in the asthenosphere. The predicted rate of present uplift at the center of the desiccated lake is 0.06 mm/yr and 0.03 mm/yr for the shallow channel and uniform mantle models, respectively. These values are beyond the first-order leveling accuracies, and the question of the existence of a narrow channel in the region cannot be resolved with the available observations.