El Dorado

El Dorado is the county seat of Union County in south central Arkansas and a center for oil production and refining.

El Dorado was laid out and platted in 1868. The name is of Spanish origin meaning "golden land". El Dorado was incorporated in 1870.

In 1877, the Florence, El Dorado, and Walnut Valley Railroad Company built a branch line from Florence to El Dorado; in 1881 it was extended to Douglass, and later to Arkansas City. The line was leased and operated by the Atchison, Topeka, and Santa Fe Railway. The line from Florence to El Dorado was abandoned in 1942.The original branch line connected Florence, Burns, De Graff, El Dorado, Augusta, Douglass, Rock, Akron, Winfield, and Arkansas City.

In 1915, the El Dorado Oil Field was the first oil field that was found using science/geologic mapping, and part of the Mid-Continent oil province. By 1918, the El Dorado Oil Field was the largest single-field producer in the United States and was responsible for 12.8% of national oil production and 9% of world production. It was deemed by some as "the oil field that won World War I".

In 1943, German and Italian prisoners of World War II were brought to Kansas and other Midwest states as a means of solving the labor shortage caused by American men serving in the war effort. Large internment camps were established in Kansas: Camp Concordia, Camp Funston (at Fort Riley), and Camp Phillips (at Salina under Fort Riley). Fort Riley established 12 smaller branch camps, including El Dorado. Prisoners commonly volunteered to help work on local farms; this enabled them to spend time outside the camp, socialize and eat better food than that provided by prison guards. In some cases, smaller structures constructed by the work details still stand.