El Dorado, city, seat (1843) of Union county, southern Arkansas, U.S., 100 miles (160 km) south of Little Rock. The site was selected in 1843 by county commissioners Robert Black, John Hampton, and Green Newton, who were instructed to locate centrally the county seat. Its Spanish name (meaning “place of riches”) was supposedly given by Matthew Rainey, a storekeeper and the town’s first settler. Lumber and cotton were the basic products before oil was discovered in 1921 in the Busey Well, resulting in an economic boom. Oil production and refining, petrochemicals, poultry products, financial services, and timber are now major industries. Conservation methods pioneered in the nearby Shuler Field have been adopted nationwide by the oil industry.
A wide variety of native flora and fauna are protected within the South Arkansas Arboretum, nestled in the heart of the city. Moro Bay State Park is to the northeast, and Felsenthal National Wildlife Refuge (102 square miles [263 square km]), with the world’s largest greentree reservoir (area of timber seasonally flooded to attract waterfowl), is to the southeast. Inc. town, 1845; city, 1905. Pop. (2000) 21,530; (2010) 18,884.