Mount Vernon is the principal city of the Mount Vernon Micropolitan Statistical Area, which includes all of Jefferson and Hamilton counties.
As of the 2000 census , there were 16,269 people, 6,988 households and 4,157 families residing in the city. The population density was 1,412.1 people per square mile (545.3/km²). There were 7,814 housing units at an average density of 678.2/sq mi (261.9/km²). The racial makeup of the city was 84.25% White, 12.36% African American, 0.17% Native American, 0.77% Asian, 0.02% Pacific Islander, 0.47% from other races and 1.97% from two or more races. Hispanic or Latino of any race were 1.49% of the population.
There were 6,988 households out of which 27.4% had children under the age of 18 living with them, 42.1% were married couples living together, 13.9% had a female householder with no husband present and 40.5% were non-families. 35.9% of all households were made up of individuals and 16.7% had someone living alone who was 65 years of age or older. The average household size was 2.25 and the average family size was 2.92.
In the city the population was spread out with 24.7% under the age of 18, 9.1% from 18 to 24, 24.9% from 25 to 44, 21.9% from 45 to 64 and 19.3% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 84.7 males. For every 100 females age 18 and over, there were 80.4 males.
The median income for a household in the city was $28,145 and the median income for a family was $36,660. Males had a median income of $31,569 versus $20,198 for females. The per capita income for the city was $16,268. About 13.0% of families and 17.1% of the population were below the poverty line, including 20.5% of those under age 18 and 12.9% of that age 65 or over.