Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Eldorado is a city in Saline County, Illinois, United States. The population was 4,122 at the 2010 census, with a 1925 peak of 8,000. Although the city's name is spelled as if it were Spanish, the name was originally "Elder-Reado" -- a combination of the last names of the town's two founders, Judge Samuel Elder and Joseph Read. According to legend, a signpainter for the railroad painted the name "Eldorado" on the train depot; as a result, the spelling and pronunciation was forever changed.