Record of early earthquakes in Northeastern United States provide limited information on effects in pennsylvania until 1737, 55 years after the first permanent settlement was established. A very severe earthquake that centered in the St.Lawrence River region in 1663 may have been felt in Pennsylvania, but historical accounts are not definite. Likewise, a damaging shock at Newbury, Mass., in 1727 probably affected towns in Pennsylvania. A strong earthquake on December 18, 1737, toppled chimneys at New York City and was reported felt at Boston, Mass., Philadelphia, Pa. and New Castle, Del. Other shocks with origins outside the State were felt in 1758, 1783, and 1791. Since 1800, when two earthquakes (March 17 and November 29) were reported as "severe" at Philadelphia, 16 tremors of intensity V or greater (Modified Mercalli Scale) have originated within the State. On November 11 and 14, 1840, sever earthquakes at Philadelphia were accompnaied by a great and unusual swell on the Delaware River.
