Alpha was incorporated as a borough by an Act of the New Jersey Legislature on April 27, 1911, from portions of Pohatcong Township, based on the results of a referendum held on May 31, 1911.
Alpha is one of the eastern-most locations within the Lehigh Valley region of Pennsylvania and New Jersey.
As of the census of 2000, there were 2,482 people, 989 households, and 688 families residing in the borough. The population density was 1,462.0 people per square mile (563.7/km²). There were 1,034 housing units at an average density of 609.1/sq mi (234.8/km²). The racial makeup of the borough was 97.06% White, 0.28% African American, 0.04% Native American, 1.21% Asian, 0.64% from other races, and 0.77% from two or more races. Hispanic or Latino of any race were 1.89% of the population.
There were 989 households out of which 31.2% had children under the age of 18 living with them, 54.6% were married couples living together, 11.0% had a female householder with no husband present, and 30.4% were non-families. 26.9% of all households were made up of individuals and 13.7% had someone living alone who was 65 years of age or older. The average household size was 2.50 and the average family size was 3.05.
In the borough the population was spread out with 24.4% under the age of 18, 6.0% from 18 to 24, 31.3% from 25 to 44, 20.7% from 45 to 64, and 17.5% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 94.8 males. For every 100 females age 18 and over, there were 90.1 males.
The median income for a household in the borough was $42,209, and the median income for a family was $45,435. Males had a median income of $39,957 versus $26,576 for females. The per capita income for the borough was $20,104. About 5.5% of families and 7.6% of the population were below the poverty line, including 14.1% of those under age 18 and 9.7% of those age 65 or over.