It was first known as "Number Six" in a line of settlements running between the Merrimack and Connecticut rivers. In 1752, the Masonian Proprietors granted the land to Andrew Todd, who called it "Todd's Town". Settled in 1761 by James Peter, it was dubbed "New Marlborough" by others from Marlboro, Massachusetts. Incorporated in 1768 by Governor John Wentworth, the town was named for Sir John Henniker, a London merchant of leather and fur, with shipping interests in Boston and Portsmouth. In the 19th century Henniker had a high rate of congenital deafness, and its own sign language, which may have played a significant role in the emergence of American Sign Language. Farmers found the town's surface relatively even, with fertile soil. Various mills operated by water power on the Contoocook River, including a woolen factory. By 1859, the population was 1,688. But mills in Henniker were closed in 1959 by the Hopkinton-Everett Lakes Flood Control Project. The Edna Dean Proctor Bridge, a stone double-arch bridge spanning the Contoocook, was built in 1835. A building for Henniker Academy was constructed of split granite in 1836. Beginning in the late 1800s, the river's scenic beauty attracted tourism. The game of paintball originated in Henniker in 1981.
Geography
According to the United States Census Bureau, the town has a total area of, of which is land and is water, comprising 1.52% of the town. The village of Henniker, or census-designated place, has a total area of, all land. Craney Hill, elevation above sea level and home of Pat's Peak ski area, is in the south. The highest point in Henniker is an unnamed summit near the town's northwest corner, with an elevation of. Henniker is drained by the Contoocook River and Amey Brook; the town lies fully within the Merrimack Riverwatershed. Henniker is crossed by U.S. Route 202, and state routes 9 and 114.
As of the census of 2010, there were 4,836 people, 1,780 households, and 1,124 families residing in the town. There were 1,928 housing units, of which 148, or 7.7%, were vacant. The racial makeup of the town was 95.7% white, 1.2% African American, 0.4% Native American, 1.1% Asian, 0.0% Native Hawaiian or Pacific Islander, 0.5% some other race, and 1.1% from two or more races. 1.7% of the population were Hispanic or Latino of any race. Of the 1,780 households, 30.3% had children under the age of 18 living with them, 49.2% were headed by married couples living together, 9.5% had a female householder with no husband present, and 36.9% were non-families. 26.3% of all households were made up of individuals, and 7.1% were someone living alone who was 65 years of age or older. The average household size was 2.41, and the average family size was 2.91. 541 residents, or 11.3% of the population, lived in group quarters rather than households. In the town, 19.1% of the population were under the age of 18, 21.3% were from 18 to 24, 20.1% from 25 to 44, 30.5% from 45 to 64, and 9.0% were 65 years of age or older. The median age was 35.2 years. For every 100 females, there were 102.0 males. For every 100 females age 18 and over, there were 99.5 males. For the period 2011-2015, the estimated median annual income for a household was $67,197, and the median income for a family was $80,845. Male full-time workers had a median income of $67,755 versus $49,677 for females. The per capita income for the town was $28,377. 10.3% of the population and 3.3% of families were below the poverty line. 12.8% of the population under the age of 18 and 5.5% of those 65 or older were living in poverty.
