Granted in 1766 by Colonial Governor Benning Wentworth, this town was named in honor of his close friend, British Admiral Washington Shirley, Viscount Tamworth. The admiral's daughter, Selina Shirley, was instrumental in the founding of Dartmouth College. The village of Whittier, like Mount Whittier in Ossipee, is named for the poet John Greenleaf Whittier.
The Chinook Kennels here raised sled dogs for the Rear Admiral Richard E. Byrd Antarctic expeditions and the Army's search-and-rescue units. The Barnstormers Theatre summer playhouse was established here in 1931 by Francis Grover Cleveland, son of President Cleveland. He supported the theatre until his death in 1995. Barnstormers is hailed as the oldest continuously running professional theatre in the state.
According to the United States Census Bureau, the town has a total area of , of which is land and is water, comprising 1.35% of the town. Tamworth is drained by the Bearcamp, Chocorua and Wonalancet rivers. Chocorua Lake is to the north. The highest point in Tamworth is the summit of Black Snout Mountain at above sea level, located precisely at the southwest corner of the town, within the Ossipee Mountain range.
As of the census of 2000, there were 2,510 people, 1,074 households, and 675 families residing in the town. The population density was 41.9 people per square mile (16.2/km²). There were 1,662 housing units at an average density of 27.7/sq mi (10.7/km²). The racial makeup of the town was 98.05% White, 0.16% African American, 0.24% Native American, 0.20% Asian, 0.36% from other races, and 1.00% from two or more races. Hispanic or Latino of any race were 0.64% of the population.
There were 1,074 households out of which 29.1% had children under the age of 18 living with them, 50.7% were married couples living together, 7.6% had a female householder with no husband present, and 37.1% were non-families. 28.7% of all households were made up of individuals and 11.2% had someone living alone who was 65 years of age or older. The average household size was 2.33 and the average family size was 2.86.
In the town the population was spread out with 23.7% under the age of 18, 6.3% from 18 to 24, 28.4% from 25 to 44, 26.0% from 45 to 64, and 15.7% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 103.7 males. For every 100 females age 18 and over, there were 97.1 males.
The median income for a household in the town was $35,200, and the median income for a family was $41,121. Males had a median income of $30,389 versus $23,352 for females. The per capita income for the town was $17,961. About 7.1% of families and 9.5% of the population were below the poverty line, including 8.2% of those under age 18 and 10.1% of those age 65 or over.