Claremont is the only city in Sullivan County, New Hampshire, United States. The population was 13,355 at the 2010 census, and in 2018 the population was estimated at 12,967.
The city is in western Sullivan County and is bordered to the west by the Connecticut River, the boundary between New Hampshire and Vermont. According to the United States Census Bureau, the city has a total area of 44.1 square miles (114.2 km), of which 43.1 square miles (111.7 km) is land and 0.97 square miles (2.5 km) is water, comprising 2.19% of the town. The Sugar River flows from east to west through the center of Claremont and empties into the Connecticut. The highest point in the city is the summit of Green Mountain, at 2,018 feet (615 m) above sea level in the northeastern part of the city. Claremont lies fully within the Connecticut River watershed.
As of the census of 2010, there were 13,355 people, 5,697 households, and 3,461 families residing in the city. The population density was 309.9 people per square mile (119.6/km). There were 6,293 housing units at an average density of 146.0 per square mile (56.3/km). The racial makeup of the city was 95.9% White, 0.6% African American, 0.3% Native American, 0.9% Asian, 0.03% Pacific Islander, 0.4% some other race, and 1.8% from two or more races. Hispanic or Latino of any race were 1.3% of the population.
There were 5,697 households, out of which 28.6% had children under the age of 18 living with them, 42.1% were headed by married couples living together, 13.0% had a female householder with no husband present, and 39.2% were non-families. 30.8% of all households were made up of individuals, and 11.8% were someone living alone who was 65 years of age or older. The average household size was 2.31, and the average family size was 2.83.
In the city, the population was spread out with 22.0% under the age of 18, 8.0% from 18 to 24, 26.0% from 25 to 44, 28.7% from 45 to 64, and 15.4% who were 65 years of age or older. The median age was 40.6 years. For every 100 females, there were 95.4 males. For every 100 females age 18 and over, there were 93.1 males.
For the period 2009–13, the estimated median annual income for a household in the city was $42,236, and the median income for a family was $51,259. Male full-time workers had a median income of $43,261 versus $35,369 for females. The per capita income for the city was $22,773. About 13.3% of families and 15.9% of the population were below the poverty line, including 22.2% of those under age 18 and 5.3% of those aged 65 or over.