The earthquake in 1791 was Connecticut’s biggest earthquake up to that time. The earthquake hit east of New Haven and did extensive damage in the East Haddam Region of the Connecticut River.
On May 16, 1791, along the lower reaches of the Connecticut River, east of New Haven, the state experienced its biggest earthquake up to that time. The felt intensity was 7 as based on the Modified Mercalli Scale, a measure that is similar to the Richter Scale but different in that it takes account of the effect of an earthquake rather than its power at source. In many older records of earthquakes all we have are accounts of the damage that was done. From these we can estimate its intensity on the Modified Mercalli Scale. The area affected by this earthquake is in and around East Haddam. It has a history of frequent earthquakes extending back to earliest settlement times.
The East Haddam region on the Connecticut River is known in Indian lore as a place of noises, presumably the noises of earthquakes. The first reported earthquake began on May 16 with two heavy shocks in quick succession. Stone walls were shaken down, tops of chimneys were knocked off, and latched doors were thrown open. A fissure several meters long formed in the ground. In a short time, thirty lighter shocks and more than one hundred other aftershocks continued during the night. Both the earthquake of May 16 and the many aftershocks were heard in Boston, Massachusetts, and in New York City.