The Spanish "El Dorado" is a widely used place name. El Dorado is home to the El Dorado Correctional Facility, which currently houses BTK killer Dennis Rader.
El Dorado's population was estimated to be 12,718 in the year 2006, a decrease of 99, or -0.8%, over the previous six years.
As of the U.S. Census in 2000, there were 12,057 people, 5,068 households, and 3,182 families residing in the city. The population density was 1,894.1 people per square mile (730.8/km²). There were 5,460 housing units at an average density of 857.7/sq mi (330.9/km²). The racial makeup of the city was 94.32% White, 1.37% Black or African American, 1.07% Native American, 0.22% Asian, 0.07% Pacific Islander, 1.06% from other races, and 1.89% from two or more races. Hispanic or Latino of any race were 2.93% of the population.
There were 5,068 households out of which 30.4% had children under the age of 18 living with them, 48.3% were married couples living together, 10.6% had a female householder with no husband present, and 37.2% were non-families. 31.9% of all households were made up of individuals and 14.2% had someone living alone who was 65 years of age or older. The average household size was 2.33 and the average family size was 2.94.
In the city the population was spread out with 25.2% under the age of 18, 10.4% from 18 to 24, 26.6% from 25 to 44, 20.1% from 45 to 64, and 17.7% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 91.8 males. For every 100 females age 18 and over, there were 87.0 males.
The median income for a household in the city was $33,098, and the median income for a family was $40,461. Males had a median income of $31,648 versus $21,806 for females. The per capita income for the city was $18,458. About 10.4% of families and 13.5% of the population were below the poverty line, including 17.7% of those under age 18 and 6.1% of those age 65 or over.