Bardonia is named for the Bardon brothers - John and the twins Phillip and Conrad - who came from Bavaria in 1849 and opened several businesses. The Bardonia railroad station, which no longer exists, was opened there in 1875.
According to the United States Census Bureau, the CDP has a total area of 2.9 square miles (7.5 km2), of which 2.6 square miles (6.7 km2) is land and 0.3 square miles (0.8 km2) (11.42%) is water.
At the 2012 census,[5] there were 4,367 people, 1,450 households and 1,189 families residing in the CDP. The population density was 1,704.6 inhabitants per square mile (658.1/km2). There were 1,468 housing units at an average density of 573.0 per square mile (221.2/km2). The racial makeup of the CDP was 87.54% white, 1.53% African American, .23% Native American, 7.88% Asian, 1.4% from other races, and 1.42% from two or more races. Hispanic or Latino of any race were 5.15% of the population.
There were 1,450 households, of which 38.1% had children under the age of 18 living with them, 72.7% were married couples living together, 7.0% had a female householder with no husband present, and 18.0% were non-families. 15.9% of all households were made up of individuals, and 9.6% had someone living alone who was 65 years of age or older. The average household size was 3.01 and the average family size was 3.37.
Age distribution was 25.2% under the age of 18, 7.1% from 18 to 24, 23.8% from 25 to 44, 31.0% from 45 to 64, and 12.9% who were 65 years of age or older. The median age was 41 years. For every 100 females, there were 94 males. For every 100 females age 18 and over, there were 90.8 males.
The median household income was $96,068, and the median family income was $104,415. Males had a median income of $70,060 versus $43,700 for females. The per capita income for the CDP was $37,677. About .8% of families and 1.4% of the population were below the poverty line, including 2.3% of those under age 18 and 1.4% of those age 65 or over. Bardonia (within Clarkstown) was the 2nd safest town in the U.S in a recent study.[citation needed]
Bardonia was previously served by the New Jersey and New York Railroad's New City Branch,[7] which was later incorporated into the Erie Railroad system. Service along the New City Branch ended in 1939, and the tracks were quickly removed thereafter. The old Bardonia railway station house existed in its place near the corner of Bardonia Road and New York State Route 304 until 2014,[8] when it was demolished to make way for a CVS.