This town was one of the fort towns established by Governor Belcher of Massachusetts, and was first granted in 1734 as Lower Ashuelot to Captain Nathaniel Hammond and Ephraim Jones. In 1753, residents petitioned Governor Benning Wentworth for a grant under authority of the New Hampshire government, since they had settled and been making improvements for over 18 years. The town was chartered that year as Swanzey, the name being suggested by Governor Brenton of Rhode Island, who owned land at Brenton's Farm (Litchfield), and Swansea, Massachusetts. There are four covered bridges located in Swanzey: Carleton, Thompson, Slate, and Cresson.
Population change for Swanzey totaled 3,490 over 56 years, from 3,626 in 1960 to 7,116 in 2016. The largest decennial percent change was an increase of 22 percent between 1970 and 1980; the smallest, a six percent increase between 2000 and 2010. The 2016 Census estimate for Swanzey was 7,116 residents, which ranked 45th among New Hampshire's incorporated cities and towns.(info from NHES website)