The authors report the first exposure of prehistoric salt-working in the Pacific, one that used solar evaporation of sea water on large flanged clay dishes. This short-lived industry of the seventh century AD disappeared beneath the dunes, but its documented nineteenth- and twentieth-century successors offer it many useful analogies: the salt, now extracted by boiling brine, was supplied to inland communities upriver, where it functioned as a prime commodity for prestige and trade and an agent of social change.