This article examines the archaeological effects of two major geologic factors, eustatic sea-level rise and land subsidence, on the archaeological site distributions of low-energy coastlines. It describes an inexpensive, quick approach to identify these effects, which exploits the interpretive value of state-maintained archaeological site location files. The application of this approach to the Mississippi Gulf Coast suggests that coastal sites older than roughly 3500 B.P. were submerged or destroyed by eustatic sea-level rise; more recent sites were affected little by this process. Among subsidence factors, endogenic or deep-earth subsidence has had little impact on local site distributions. Exogenic or surficial subsidence processes, however, are sufficient to explain the temporal gradient of tidally inundated marsh sites.