El Dorado, also known as Mud Springs, was a trading post, emigrant stop, and mining camp in the 1850’s. It later became one of the remount stations of the Central Overland Pony Express. At the Nevada House on April 13, 1860, pony rider William (Sam) Hamilton changed horses while carrying the first west-bound mail of the Pony Express from St. Joseph, Missouri, to Sacramento, California.