Pedestrian survey of the middle Sama Valley (460-730 masl), Tacna, on the far south coast of Peru has identified 47 archaeological sites dating from the Archaic to the Late Horizon Period. Early hunter-gatherer populations occupied lomas and riparian environments in connection with coastal-highland mobility. The arrival of agropastoralist Cabuza populations in the terminal Middle Horizon foreshadowed Murra’s (1972) early Colonial “vertical complementarity” mode. Throughout the late prehispanic period a series of highlander incursions into the valley occurred attracted by the arable valley, lomas pasture, and proximity to the coast, culminating in the installation of Inca imperial infrastructure.