Butte was, in its heyday, one of the largest and most notorious copper boomtowns in the American West, home to hundreds of saloons and a famous red-light district called 'The Line'.
Butte started out as a mining town in the late 19th century. It lies in the Silver Bow Creek Valley (or Summit Valley), a natural bowl sitting high in the Rockies and straddling the Continental Divide. Gold, silver and copper were mined in the area, and the small town soon became one of the most prosperous cities in the country, especially during World War I. It was called "the Richest Hill on Earth".
The prosperity lasted until the 1950s, when the declining grade of ore and competition from other mines led the Anaconda company to switch its focus from the costly and dangerous practice of underground mining to open pit mining.
Creation of the Berkeley Pit, which opened in 1955, required the destruction of thousands of homes. At the time, it was the largest truck-operated open pit copper mine in the United States. In 1982, all mining in the Berkeley Pit was suspended. When mining shut down, water pumps in nearby mines were also shut down, which resulted in highly acidic water laced with toxic heavy metals filling up the pit. Only two years later the pit was classified as a Superfund site and an environmental hazard site. 342 migrating geese died after stopping at the pit. Steps have since been taken to prevent a recurrence, including loudspeakers broadcasting sounds to scare off waterfowl. In November 2003 the Horseshoe Bend treatment facility began treating and diverting much of the water that would have flowed into the pit.
The Berkeley Pit is one of the city's biggest tourist attractions.