El Dorado (pronounced to rhyme with tornado is a city in Union County, Arkansas, USA. According to 2006 Census Bureau estimates, the population of the city is 20,467. The city is the county seat of Union County, and home to the headquarters of Murphy Oil Corporation, Deltic Timber Corporation, and Lion Oil Refinery. The city hosts a community college, South Arkansas Community College, as well as a symphony and an arts center. Most recently, El Dorado has become a community of education with the January 2007 announcement by Murphy Oil Corporation of the El Dorado Promise, a scholarship program that allows all El Dorado High School graduates who have been at the school since at least the ninth grade to attend any college in the country of their choice.