Oak Ridge was established in the early 1940s as a base for the Manhattan Project— the massive U.S. government operation that developed the atomic bomb. As such, scientific development still plays a crucial role in the city's economy and culture in general.
As of the census of 2000, there were 27,387 people, 12,062 households, and 7,695 families residing in the city. The population density was 320.1 people per square mile (123.6/km²). There were 13,417 housing units at an average density of 156.8/sq mi (60.6/km²). The racial makeup of the city was 86.96% White, 8.18% African American, 0.30% Native American, 2.10% Asian, 0.02% Pacific Islander, 0.76% from other races, and 1.68% from two or more races. Hispanic or Latino of any race were 1.93% of the population.
There were 12,062 households out of which 26.8% had children under the age of 18 living with them, 49.7% were married couples living together, 11.1% had a female householder with no husband present, and 36.2% were non-families. 32.7% of all households were made up of individuals and 15.0% had someone living alone who was 65 years of age or older. The average household size was 2.24 and the average family size was 2.83.
In the city the population was spread out with 22.4% under the age of 18, 6.6% from 18 to 24, 23.6% from 25 to 44, 26.3% from 45 to 64, and 21.1% who were 65 years of age or older. The median age was 43 years. For every 100 females there were 88.1 males. For every 100 females age 18 and over, there were 83.4 males.
The median income for a household in the city was $41,950, and the median income for a family was $57,087. Males had a median income of $45,149 versus $27,500 for females. The per capita income for the city was $24,793. About 8.0% of families and 10.9% of the population were below the poverty line, including 17.5% of those under age 18 and 5.5% of those age 65 or over.