Plattsburgh is a city in and the seat of Clinton County, New York, United States. The population was 19,989 at the 2010 census. The population of the unincorporated areas within the surrounding (and separately incorporated) Town of Plattsburgh was 11,870 as of the 2010 census, making the combined population for all of Plattsburgh to be 31,859. Plattsburgh lies just to the northeast of Adirondack Park, immediately outside of the park boundaries. It is the second largest community in the North Country region (after Watertown), and serves as the main commercial hub for the sparsely populated northern Adirondack Mountains.
As of the census of 2010, there were 19,989 people, 7,600 households, and 3,473 families residing in the city.
The population density was 3,919.4 people per square mile (1,525.9/km²). There were 8,691 housing units at an average density of 1704.1/sq mi (663.4/km²). The racial makeup of the city was 89.88% White, 3.5% Black or African American, 0.38% Native American, 2.77% Asian, 0.03% Pacific Islander, 1.03% from other races, and 2.41% from two or more races. Hispanic or Latino of any race were 3.4% of the population.
There were 7,600 households out of which 22.3% had children under the age of 18 living with them, 31.1% were married couples living together, 11.4% had a female householder with no husband present, and 54.3% were non-families. 40.4% of all households were made up of individuals and 13.5% had someone living alone who was 65 years of age or older. The average household size was 2.10 and the average family size was 2.83.
In the city, the population was spread out with 16.5% under the age of 18, 27.7% from 18 to 24, 23.5% from 25 to 44, 18.1% from 45 to 64, and 14.1% who were 65 years of age or older. The median age was 30 years. For every 100 females, there were 86.4 males. For every 100 females age 18 and over, there were 83.7 males.
The median income for a household in the city was $28,846, and the median income for a family was $46,337. Males had a median income of $35,429 versus $26,824 for females. The per capita income for the city was $17,127. About 13.6% of families and 23.1% of the population were below the poverty line, including 20.0% of those under age 18 and 13.0% of those age 65 or over.