Oklahoma City is the third largest city in the country in terms of geographic area, although its urbanized zone is 244 mi² - resulting in an urban population density more comparable to that found in other major cities, 2,515/mi² in 2004. Oklahoma City is the second largest city in the nation still in compliance with the Clean Air Act.

As of the census of 2000, there were 506,132 people, 204,434 households, and 129,406 families residing in the city. The population density was 321.9/km² (833.8/mi²) for the entire city but was more than 2600/mi² in the urbanized areas. There were 228,149 housing units at an average density of 145.1/km² (375.9/mi²). The racial makeup of the city was 60.41% White, 18.37% Black or African American, 3.51% Native American, 3.48% Asian American, 0.07% Pacific Islander, 5.28% from other races, and 3.89% from two or more races. 16.15% of the population were Hispanic or Latino of any race.

There were 204,434 households, 30.8% of which had children under the age of 18 living with them. The average household size was 2.41 and the average family size was 3.04. The median age was 34 years. For every 100 females there were 95.6 males. For every 100 females age 18 and over, there were 92.7 males.

The median income for a household in the city was $34,947, and the median income for a family was $42,689. These figures are among the lowest in the nation for a city of this size, but the cost of living is considerably below the national average. Financial progress is actually higher than the national average, and on top of that, the metro is a pretty good bargain for the amenities available. Males had a median income of $31,589 versus $24,420 for females. The per capita income for the city was $19,098. 16.0% of the population and 12.4% of families were below the poverty line. Out of the total population, 23.0% of those under the age of 18 and 9.2% of those 65 and older were living below the poverty line.

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