This town was carved out of portions of Gilsum, Stoddard, Packersfield (Nelson), and Keene, when residents of remote parts of each town petitioned for an incorporated town that would be more central to all. It was named in honor of General John Sullivan, a Revolutionary War hero, who was elected President of New Hampshire in 1786. The town of Sullivan was incorporated the following year. General Sullivan served as a member of the Continental Congress, Adjutant General to Washington, and Major General of the Northern Army before becoming president of the state.
Population change for Sullivan totaled 406 over 56 years, from 261 in 1960 to 667 in 2016. The largest decennial percent change was an increase of 56 percent between 1970 and 1980, which followed a 44 percent increase over the previous decade. The 2016 Census estimate for Sullivan was 667 residents, which ranked 210th among New Hampshire's incorporated cities and towns. (info from NHES website)