Mercur is a historical hard rock mining ghost town located at in Tooele County, Utah. In 1891, It became site of the first successful use of the cyanide process of gold extraction in the United States, the dominant metallurgy today.

The town first came into being in 1870 as Lewiston, when gold was discovered at the head of the Lewiston Canyon, six miles west of present-day Cedar Fort. A small gold rush began, peaking about 1873; the population reached as high as 2000. During the mid-1870s, silver boomed, and silver mines were opened and quartz mills to process the ore were built. A million dollars worth of silver bullion was shipped down the valley, but the ore quickly gave out, and Lewiston became a ghost town by 1880.

In 1879, a Bavarian miner named Arie Pinedo had discovered a deposit of cinnabar in the area. The ore contained gold as well as mercury, but contemporary processes were unable to extract it. Similar discoveries were made throughout the 1880s. In 1890, a group of Nebraska "farmers" bought the Mercur claim through an over optimistic promoter. They opened the mine and put in a basic amalgamation mill, a grand flop. Mercur ores were not workable with the ancient process. One of the Nebraska partners, Gilbert S. "Gill" Peyton, a former druggist, heard of the new but unperfected cyanide process and gave it a try. Fearful of losing his and his relatives investment, he solved the difficulties of the new method on the ores, and by December 1891 proved that the cyanide process worked -- the first such successful operation in the United States (The cyanide process has come to dominate western gold metallurgy). As a result, Peyton and his brother-in-law, partner Hal Brown became rich, as did others of the Nebraska group.

By 1916, there was only one building left in Mercur, and, by 1930, it was gone. The nearby Mercur Gold Mine was re-opened by Barrick Gold in 1985, and is an open pit mine located over the original town of Mercur. Only the Mercur Cemetery remains from the original town. No legible headstones in the cemetery are visible today.