Butte, Montana, earned the nickname “The Richest Hill on Earth” due to the massive, geologically rich ore body beneath the city. This resource became a global source of industrial metals during the late 19th and early 20th centuries. Driven by the worldwide need for electricity, the scale of operations transformed Butte from a remote mining camp into one of the largest and most prosperous cities in the American West.
The Primary Resource: Copper
Copper became the defining mineral of Butte’s economic boom, supplying the metal that powered the world’s electrical age. Although initial finds were gold and silver, the vast, deep deposits of copper sulfide ores, such as chalcocite and covellite, proved most valuable. This shift began in the 1880s when Marcus Daly recognized the potential of the copper lodes. Daly founded the Anaconda Copper Mining Company, which grew into one of the world’s largest corporations.
The scale of copper production was unprecedented for a single mining district in the United States. By 1896, the five square miles of the Butte Hill were producing approximately 26% of the world’s copper supply and over half of the U.S. total output. This volume was fueled by the global electrification movement, which created a high demand for copper wiring and components. In 1910 alone, Butte mines yielded 284 million pounds of copper, cementing the city’s status as the largest copper producer in North America.
The copper sulfide ores required sophisticated processing, leading to the construction of massive facilities. The Anaconda smelter, built 26 miles west of Butte, was one of the largest metallurgical plants in the world, processing ore from numerous underground shafts. The deep, rich copper veins were the source of immense wealth for nearly a century. Over its history, the Butte mining district produced more than 21 billion pounds of copper.
Secondary Metals Extracted
Although copper was the primary engine of wealth, Butte’s unique geology allowed for the simultaneous extraction of several other valuable metals. Early prospectors were drawn to placer gold deposits discovered in the 1860s, followed by rich silver lodes in the 1870s. Silver was the initial focus of hard-rock mining and remained a significant byproduct, with over 715 million troy ounces produced through 2005.
Gold was consistently mined alongside the dominant copper and silver ores, totaling nearly 2.9 million ounces over the life of the district. The ore body’s mineralization was zoned, meaning different metals were concentrated in distinct areas around the central copper deposits. This zoning meant that mines in the intermediate and peripheral zones were rich in zinc and manganese.
Zinc became important during periods of high industrial demand, such as World War I, as a component in alloys and munitions. The district produced over 2.1 million metric tons of zinc through 2005. Manganese, often found in the outer zones, was also extracted, contributing over 1.6 million metric tons, primarily used in steel production. Other metals extracted included molybdenum, lead, and trace amounts of arsenic.
Evolution of Extraction Techniques
Extraction methods underwent a dramatic transformation, shifting from deep, selective mining to massive surface extraction. The initial century of mining (1870s through the mid-20th century) relied on extensive underground shaft mining, creating a complex web of tunnels beneath the city. Miners followed the rich, high-grade veins of copper ore, requiring a large, skilled workforce and significant safety risks.
By the 1940s and 1950s, the highest-grade, easily accessible copper veins were becoming depleted, and competition increased. The Anaconda Company responded by transitioning to large-volume, lower-cost surface mining methods. This shift began with block-caving experiments but quickly moved to open-pit mining.
The development of the Berkeley Pit, beginning in 1955, marked the most significant change in Butte’s mining history. The open-pit method allowed for the profitable extraction of vast quantities of lower-grade disseminated ore that was uneconomical via underground tunnels. This surface operation grew to be approximately one mile long, half a mile wide, and over 1,780 feet deep, consuming much of the historic eastern part of the city. The pit eventually yielded about one billion tons of material.
Modern Status and Remediation
Large-scale historical mining in Butte has ceased, shifting the focus to environmental management and limited, modern extraction. The Berkeley Pit closed in 1982, and when deep water pumps were turned off, the pit and interconnected underground workings began to fill with groundwater. This created a vast, acidic lake laden with high concentrations of dissolved heavy metals, classifying the area as a major Superfund site.
The primary environmental concern is the rising level of the toxic water, which must be kept below a critical point to prevent contamination of surrounding groundwater and Silver Bow Creek. The Horseshoe Bend Facility, a water treatment plant, operates continuously, treating millions of gallons daily to remove heavy metals and neutralize acidity. This ongoing remediation effort is federally mandated to protect public health and the environment.
While the massive Anaconda Company operations are history, mining continues in Butte. Montana Resources operates the Continental Pit, an open-pit mine near the Berkeley Pit, primarily extracting copper and molybdenum. The city’s modern economy is increasingly defined by its historical legacy, with tourism centered on preserved mining artifacts and the unique status of the Berkeley Pit.