According to the United States Census Bureau, the township has a total area of 12.9 square miles (33 km2), of which 12.8 square miles (33 km2) is land and 0.2 square miles (0.52 km2), or 1.16%, is water. The township encircles the borough of Hanover on three sides, with the York County-Adams County boundary forming the western border of both the township and the borough.
As of the census of 2000, there were 14,592 people, 5,421 households, and 4,103 families residing in the township. The population density was 1,144.2 people per square mile (441.9/km²). There were 5,643 housing units at an average density of 442.5/sq mi (170.9/km²). The racial makeup of the township was 97.46% White, 0.49% African American, 0.17% Native American, 0.82% Asian, 0.02% Pacific Islander, 0.47% from other races, and 0.58% from two or more races. Hispanic or Latino of any race were 1.05% of the population.
There were 5,421 households out of which 36.1% had children under the age of 18 living with them, 63.2% were married couples living together, 8.4% had a female householder with no husband present, and 24.3% were non-families. 19.7% of all households were made up of individuals and 7.4% had someone living alone who was 65 years of age or older. The average household size was 2.63 and the average family size was 3.02.
In the township the population was spread out with 25.9% under the age of 18, 6.4% from 18 to 24, 30.7% from 25 to 44, 22.4% from 45 to 64, and 14.6% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 95.9 males. For every 100 females age 18 and over, there were 92.6 males.
The median income for a household in the township was $47,876, and the median income for a family was $53,544. Males had a median income of $38,415 versus $24,024 for females. The per capita income for the township was $19,833. About 2.3% of families and 3.6% of the population were below the poverty line, including 3.8% of those under age 18 and 4.7% of those age 65 or over.