Originally named Mill City, the name was changed to Dumont in 1880 in honor of Colonel John M. Dumont, a pioneer and influential mining man in the county. At one time, Colonel Dumont owned three mines – the Whale, Freemont, and Lincoln mines. Today, the Stanley Mine is located on the site of the old Whale Mine.
Dumont/Mill City was once an important stage coach stop known for its ore stamping mills and smelting enterprises. In the early days of mining, the ore was crushed by Spanish arastres powered by mules and water. An example of this primitive technology can be seen in front of the Idaho Springs Library.
Dumont was home to around 100 people and consisted of two hotels, a general store, a school, and a firehouse. The Mill City House, built in 1860 still stands as does the Dumont School which was erected in 1909. The stagecoach stop was located at the Mill City House and housed the first saloon west of Denver as well as the first Singer sewing machine in the territory. In fact, President Ulysses S. Grant once stayed at the Mill City House. When I-70 was built, much of the southern half of the city was sacrificed to create the highway.