Manalapan Township was formed by an Act of the New Jersey Legislature on March 9, 1848, from portions of Freehold Township. Englishtown was formed as a borough from portions of Manalapan on January 4, 1888, based on the results of a referendum held the previous day.
Yorketown (2000 Census population of 6,712) is a census-designated place and unincorporated area located within Manalapan Township.
The Battle of Monmouth was fought in Monmouth Battlefield State Park, which is in Freehold Township and Manalapan.
As the census of 2000, there were 33,423 people, 10,781 households, and 9,002 families residing in the township. The population density was 1,084.6 people per square mile (418.7/km²). There were 11,066 housing units at an average density of 359.1/sq mi (138.6/km²). The racial makeup of the township was 91.81% White, 1.99% African American, 0.03% Native American, 4.53% Asian, 0.01% Pacific Islander, 0.53% from other races, and 1.10% from two or more races. Hispanic or Latino of any race were 3.54% of the population. Manalapan has large Italian and Jewish communities.
There were 10,781 households out of which 47.0% had children under the age of 18 living with them, 75.9% were married couples living together, 5.7% had a female householder with no husband present, and 16.5% were non-families. 14.9% of all households were made up of individuals and 10.4% had someone living alone who was 65 years of age or older. The average household size was 3.09 and the average family size was 3.45.
In the township the population was spread out with 30.3% under the age of 18, 5.8% from 18 to 24, 27.7% from 25 to 44, 24.5% from 45 to 64, and 11.6% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 92.2 males. For every 100 females age 18 and over, there were 89.5 males.
The median income for a household in the township was $83,575, and the median income for a family was $94,112 (these figures had risen to $102,882 and $114,124 respectively as of a 2007 estimate). Males had a median income of $72,198 versus $39,921 for females. The per capita income for the township was $32,142. About 3.2% of families and 3.8% of the population were below the poverty line, including 5.1% of those under age 18 and 5.7% of those age 65 or over.