According to the United States Census Bureau, the city has a total area of 6.4 square miles (16.6 km²), of which 6.4 square miles (16.5 km²) is land and 0.1 square miles (0.2 km²), or 0.93%, is water.
There were 5,068 households out of which 30.4% had children under the age of 18 living with them, 48.3% were married couplesliving 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.
Industry
A large oil refinery, which is currently owned and operated by Frontier Oil, is situated on the southwest edge of El Dorado. It was constructed and originally owned by what would later become Skelly Oil. Later, the refinery changed hands and was rebranded after Skelly was purchased by Getty Oil and then rebranded again after Texaco attempted to purchase Getty.
The El Dorado Frontier oil refinery is one of the largest in the Plains States and in the Rocky Mountain region. Capacity is 110,000 barrels per day, with production split up into gasoline (55% of production); diesel and jet fuel (34% of production); and asphalt, chemicals and other refined petroleum products (11% percent of production).