The township shares Union County's rural character, with farms and woodlands dominating. Most of the unincarcerated population lives in the unincorporated hamlet of Allenwood. Just north of the hamlet on U.S. Route 15 is the Allenwood Federal Correctional Complex, with low, medium, and high security federal prisons. With about 4,000 inmates, these facilities contain the great majority of the township's residents.
As of the census of 2000, there were 4,687 people, 335 households, and 249 families residing in the township. The population density was 310.5 people per square mile. There were 354 housing units at an average density of 23.5/sq mi. The racial makeup of the township was 55.17% White, 36.61% African American, 0.30% Native American, 1.94% Asian, 0.04% Pacific Islander, 0.34% from other races, and 5.59% from two or more races. Hispanic or Latino of any race were 20.57% of the population. There were 335 households, out of which 34.6% had children under the age of 18 living with them, 63.9% were married couples living together, 6.0% had a female householder with no husband present, and 25.4% were non-families. 20.3% of all households were made up of individuals, and 8.7% 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 4.9% under the age of 18, 8.7% from 18 to 24, 63.3% from 25 to 44, 19.9% from 45 to 64, and 3.1% who were 65 years of age or older. The median age was 35 years. For every 100 females, there were 826.3 males. For every 100 females age 18 and over, there were 1,057.7 males. The median income for a household in the township was $36,719, and the median income for a family was $41,711. Males had a median income of $16,270 versus $22,833 for females. The per capita income for the township was $12,916. About 4.5% of families and 14.0% of the population were below the poverty line, including 5.0% of those under age 18 and 5.2% of those age 65 or over.
Government
Gregg Township is a township of the second class, governed by a board of three supervisors. The township has been zoned since 1968, with a three-member hearing board. This was the subject of a zoning battle in the early 1990s when a Texas waste company called USPCI attempted to locate a toxic waste incinerator across Route 15 from the Allenwood Penitentiary, leading to the local community to unite under the banner of the . Ultimately the rezoning for the burner was not approved and an appeal was denied. The Federal Bureau of Prisons Allenwood Federal Correctional Complex is located in the township.
