Plainfield Township, Northampton County, Pennsylvania
|Elevation||568 ft (173.1 m)|
|Area||24.8 sq mi (64.2 km2)|
|- land||24.7 sq mi (64 km2)|
|- water||0.1 sq mi (0 km2), 0.4%|
|Density||247.5 / sq mi (95.6 / km2)|
|- summer (DST)||EDT (UTC-4)|
Plainfield Township is a township in Northampton County, Pennsylvania, United States. Plainfield Township is located in the Lehigh Valley region of the state. It is part of Pennsylvania's Slate Belt .
The population of Plainfield Township was 6,138 at the 2010 census.
According to the United States Census Bureau, the township has a total area of 24.8 square miles (64 km2), of which 24.7 square miles (64 km2) is land and 0.04 square miles (0.10 km2), or 0.16%, is water. It is in the Delaware watershed and drained by Bushkill Creek and Martins Creek. Its natural northern boundary is Blue Mountain. Its villages include Belfast, Delabole, Edelman, Kesslersville, Miller, West Bangor, and West Pen Argyl. Its numbered routes are the 33 Expressway, 191, and 512.
Neighboring municipalities 
- Bushkill Township (west)
- Upper Nazareth Township (southwest)
- Stockertown (southwest)
- Forks Township (south)
- Lower Mount Bethel Township (southeast)
- Washington Township (east)
- Hamilton Township, Monroe County (north)
- Ross Township, Monroe County (northwest)
As of the census of 2000, there were 5,668 people, 2,130 households, and 1,637 families residing in the township. The population density was 229.2 people per square mile (88.5/km²). There were 2,191 housing units at an average density of 88.6/sq mi (34.2/km²). The racial makeup of the township was 98.85% White, 0.37% African American, 0.02% Native American, 0.28% Asian, 0.14% from other races, and 0.34% from two or more races. Hispanic or Latino of any race were 0.67% of the population.
There were 2,130 households out of which 30.4% had children under the age of 18 living with them, 68.0% were married couples living together, 5.6% had a female householder with no husband present, and 23.1% were non-families. 18.6% of all households were made up of individuals and 9.0% had someone living alone who was 65 years of age or older. The average household size was 2.62 and the average family size was 3.00.
In the township the population was spread out with 22.2% under the age of 18, 6.1% from 18 to 24, 27.1% from 25 to 44, 27.8% from 45 to 64, and 16.7% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 96.9 males. For every 100 females age 18 and over, there were 93.2 males.
The median income for a household in the township was $49,019, and the median income for a family was $54,856. Males had a median income of $39,334 versus $25,145 for females. The per capita income for the township was $20,639. About 1.7% of families and 3.7% of the population were below the poverty line, including 2.9% of those under age 18 and 4.9% of those age 65 or over.
Public education 
The township is served by the Pen Argyl Area School District.