In the early 20th century, archaeological research in the terp (artificial dwelling-mound) region of the northern Netherlands focused, besides settlement history, on natural salt-marsh dynamics and sea-level rise. In particular Van Giffen used salt-marsh deposits under dated terp layers to reconstruct the rate of sedimentation of the developing salt marsh and relative sea-level rise. This line of research in archaeology was rekindled during excavations in the terp of Wijnaldum-Tjitsma between 1991 and 1993. Since then, geology has become an integral part of archaeological research in the terp region. This paper focuses on the northwestern part of the province of Friesland (Westergo), where most archaeological terp research during the past three decades has been carried out, owing to several research programmes by the Province ofFriesland. The primary aim of the geoarchaeological research is to better understand the interaction between human inhabitants and the salt-marsh landscape. The sedimentary record exposed in the excavation trenches makes it possible to collect data on the development of the coastal environments of the Wadden Sea prior to habitation, including data on sea-level rise. The sea-level data collected in the geoarchaeological studies in Westergo are the topic of this paper. The measured levels of the tidal-flat/salt-marsh boundary underneath the terps make it possible to reconstruct palaeo-Mean High Water (palaeo-MHW) levels. Such sea-level index points (SLIPs), based on marine shell data points from 12 locations, now make it possible to establish a palaeo-MHW diagram for this part of the Wadden Sea, for the period between 1200 BC and AD 100. In this period the palaeo-MHW in the Westergo region rose from c.1.8m to 0.3 m −NAP: a mean sea-level rise of c.0.12 m per century. We discuss the fact that elevation of the palaeo-MHW SLIP is not only determined by relative sea level (RSL), but also by the magnitude of the tidal amplitude. The tidal range, and therefore the MHW elevations in a tidal basin, ...