Londonderry Township, Dauphin County, Pennsylvania

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For other Pennsylvania townships of the same name, see Londonderry Township, Pennsylvania.
Londonderry Township,
Dauphin County,
Three Mile Island
Location in Dauphin County and state of Pennsylvania.
Location in Dauphin County and state of Pennsylvania.
Country United States
State Pennsylvania
County Dauphin
Incorporated 1768
 • Total 26.9 sq mi (70 km2)
 • Land 22.8 sq mi (59 km2)
 • Water 4.1 sq mi (11 km2)
Population (2000)
 • Total 5,224
 • Density 229.4/sq mi (88.6/km2)
Time zone Eastern (EST) (UTC-5)
 • Summer (DST) EDT (UTC-4)
Area code(s) 717

Londonderry Township is a township in Dauphin County, Pennsylvania, United States. The population was 5,224 at the 2000 census.

The township includes the Three Mile Island Nuclear Generating Station, the location of the largest accident in the history of the American nuclear power generating industry, which took place in 1979.


Londonderry Township originally was part of Derry Township. Since the Township was so large and difficult to govern, the residents petitioned the court in 1767 to subdivide the land into two parts, the eastern section to remain Derry and the western to be Londonderry.[1] It is named after County Londonderry, in Northern Ireland.[2]

Derry and Londonderry became a part of Dauphin County when it was established in 1785. In 1787, the population of Derry Township was 198. Conewago Township was created in 1850 from southern parts of Derry Township and eastern parts of Londonderry Township.


According to the United States Census Bureau, the township has a total area of 26.9 square miles (69.6 km²), of which, 22.8 square miles (59.0 km²) of it is land and 4.1 square miles (10.6 km²) of it (15.23%) is water.


As of the census[3] of 2000, there were 5,224 people, 2,004 households, and 1,517 families residing in the township. The population density was 229.4 people per square mile (88.6/km²). There were 2,095 housing units at an average density of 92.0/sq mi (35.5/km²). The racial makeup of the township was 97.74% White, 0.77% African American, 0.10% Native American, 0.25% Asian, 0.11% from other races, and 1.03% from two or more races. Hispanic or Latino of any race were 0.67% of the population.

There were 2,004 households out of which 33.6% had children under the age of 18 living with them, 63.2% were married couples living together, 7.9% had a female householder with no husband present, and 24.3% were non-families. 20.6% of all households were made up of individuals and 7.8% had someone living alone who was 65 years of age or older. The average household size was 2.60 and the average family size was 2.99.

In the township the population was spread out with 25.1% under the age of 18, 6.3% from 18 to 24, 30.9% from 25 to 44, 25.5% from 45 to 64, and 12.2% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 96.5 males. For every 100 females age 18 and over, there were 97.0 males.

The median income for a household in the township was $42,804, and the median income for a family was $52,650. Males had a median income of $38,750 versus $27,719 for females. The per capita income for the township was $20,055. About 4.1% of families and 7.0% of the population were below the poverty line, including 8.2% of those under age 18 and 9.2% of those age 65 or over.


  1. ^
  2. ^ Notes and Queries, Historical, Biographical and Genealogical, Relating Chiefly to Interior Pennsylvania. Harrisburg Publishing Company. 1895. pp. 14–. 
  3. ^ "American FactFinder". United States Census Bureau. Retrieved 2008-01-31. 

Coordinates: 40°12′00″N 76°40′59″W / 40.20000°N 76.68306°W / 40.20000; -76.68306