Epsom New Hampshire was incorporated in 1727, and is one of seven towns granted by the Governor of Massachusetts before New Hampshire became an independent province. Epsom was named for Epsom, England, home of the Earl of Derby, whose horse racing 'derby' at Epsom Downs was famous. Epsom, England was also known for its mineral springs, the source of Epsom salts. New Hampshire's Epsom includes the village of Gossville.

Epsom's population increased above the statewide average rate over each of the last five decades. Decennial growth rates ranged from a 12 percent increase between 1990-2000 to an 87 percent increase between 1970-1980. Overall, Epsom grew more than five times larger, going from 756 in 1950 to 4,021 residents in 2000, a total increase of 3,265 residents. The 2003 Census estimate for Epsom was 4,388 residents, which ranked 80th among New Hampshire's incorporated cities and towns. Epsom contains 34.5 square miles of land area and 0.1 square miles of inland water area.