Analysis of temporal and spatial patterns in settlement between San Clemente and San Nicolas islands suggest that the trajectory of human adaptations differed significantly. On San Clemente, site densities increased dramatically during the latter portion of the late Holocene, including numerous small-sized upland residential sites targeting terrestrial resources. In contrast, occupation of San Nicolas was intensive and constant from the latter half of the middle Holocene onward, and subsistence was more marine-oriented. These divergent trends in land use intensity and settlement organization were driven in part by modest geographic and environmental differences between the islands tied to land mass, annual rainfall, and terrestrial vegetation.