El Dorado is a city in, and the county seat of, Union County, on the southern border of Arkansas, United States. According to the 2010 census, the population of the city is 18,884.El Dorado is headquarters of the Arkansas Oil and Gas Commission as well as Murphy USA, Deltic Timber Corporation and a DelekUS oil refinery. The city has a nationally-recognized downtown arts district, the Murphy Arts District (MAD); a community college, South Arkansas Community College (SouthArk); and a multi-cultural arts center, South Arkansas Arts Center (SAAC). El Dorado is the population, cultural and business center of south central Arkansas. The city was the heart of the 1920s oil boom in the area. During World War II, it became a center of the chemical industry, which still plays a part in the economy, as do oil and timber. El Dorado is located approximately 120 miles (190 km) from the state capital of Little Rock.