We present a new mean-high-water curve for Hammock River marsh, Clinton, Connecticut, obtained by improving the age model for an existing record of relative marsh elevation based on foraminiferal analysis of a 1.8-m-long peat core. Unlike the earlier curve, the new curve confirms trend changes in mean-high-water rise during the past 1400 yr as noted for salt marshes 15 km farther west, suggesting a regional cause. These trend changes and century-scale mean-high-water variations in the Clinton record correlate positively with large-scale regional variations in sea-surface and summer-air temperature, indicating a link between sea level and the climate-ocean system. On the basis of the Clinton mean-high-water curve, we conclude that real sea level oscillated centimeters to decimeters on a century time scale over the past 1400 yr, was 25 ± 25 cm higher ca. a.d. 1050 (Medieval Warm Period) than ca. a.d. 1650 (Little Ice Age), and rose at a mean rate of ∼1 mmṁyr−1 over the past 350 yr; there was little or no rise during the cool 1800s.