Figure 1 depicts the surface observations at 2:30 am EDT, which shows a cold front on the northeast coast of the United States. This front became the focus for thunderstorms in the early morning hours of December 18th, possibly aided by sea-breezes, which ultimately led to this F1 tornado.

The Essex County, MA F1 tornado of December 18, 1956 impacted Essex County in Massachusetts. According to NOAA (2019), the F1 tornado caused no fatalities or injuries, but caused $250 dollars in property damage. The tornado touched down in Essex County just west of Peter Road at 9:15 am EDT. The tornado travelled for 0.5 miles and had a maximum width of 23 yards.
Sources
NOAA Central Library. (2019). U.S. Daily Weather Maps. Tuesday December 18, 1956 [PDF]. Retrieved from https://library.noaa.gov/Collections/Digital-Collections/US-Daily-Weather-Maps
NOAA National Centers for Environmental Information (2019). Storm Events Database. Retrieved from: https://www.ncdc.noaa.gov/stormevents/