Portsmouth is a city in Rockingham County, New Hampshire, United States. As of the 2010 census it had a population of 21,233, and in 2018 the estimated population was 21,896. A historic seaport and popular summer tourist destination on the Piscataqua River bordering the state of Maine, Portsmouth was formerly the home of the Strategic Air Command’s Pease Air Force Base, since converted to Portsmouth International Airport at Pease.
According to the United States Census Bureau, the city has a total area of 16.8 square miles (43.6 km), of which 15.6 square miles (40.5 km) is land and 1.2 square miles (3.1 km), or 7.21%, is water. Portsmouth is drained by Sagamore Creek and the Piscataqua River, which is the boundary between New Hampshire and Maine. The highest point in the city is 110 feet (34 m) above sea level, within Pease International Airport.
The city is crossed by Interstate 95, U.S. Route 1, U.S. Route 4, New Hampshire Route 1A, New Hampshire Route 16, and New Hampshire Route 33. Boston is 55 miles (89 km) to the south, Portland, Maine, is 53 miles (85 km) to the northeast, and Dover, New Hampshire, is 13 miles (21 km) to the northwest.
Portsmouth is the sole city in Rockingham County, but the fourth-largest municipality, with fewer people than the towns of Derry, Londonderry, and Salem.
As of the census of 2010, there were 21,233 people, 10,014 households, and 4,736 families residing in the city. The population density was 1,361.1 people per square mile (524.4/km²). There were 10,625 housing units at an average density of 681.1 per square mile (262.3/km²). The racial makeup of the city was 91.5% White, 1.7% African American, 0.2% Native American, 3.5% Asian, 0.01% Pacific Islander, 0.7% some other race, and 2.3% from two or more races. Hispanic or Latino of any race were 2.8% of the population.
There were 10,014 households, out of which 20.2% had children under the age of 18 living with them, 35.5% were headed by married couples living together, 8.3% had a female householder with no husband present, and 52.7% were non-families. 39.2% 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 2.03, and the average family size was 2.75.
In the city, the population was spread out with 16.6% under the age of 18, 7.7% from 18 to 24, 32.2% from 25 to 44, 27.6% from 45 to 64, and 15.9% who were 65 years of age or older. The median age was 40.3 years. For every 100 females, there were 94.2 males. For every 100 females age 18 and over, there were 92.6 males.
For the period 2010–14, the city’s estimated median annual household income was $67,679, and the median family income was $90,208. Male full-time workers had a median income of $58,441 versus $45,683 for females. The city’s per capita income for the city was $42,724. About 4.0% of families and 7.6% of the population were below the poverty line, including 6.9% of those under age 18 and 7.1% of those age 65 or over.