The Big Bug district is one of the earliest mining districts formed in Central Arizona. It was named after Big Bug Creek, which was home to plentiful walnut-size beetles and runs through the foothills of the Bradshaw Mountains southeast of Prescott.
Beginning in 1863 with the discovery of gold in the creeks in the Agua Fria River basin by Joseph Walker and his prospecting party, the area became popular for both its placer and lode deposits.
The arrival of the Prescott & Eastern Railroad in 1898 allowed the district to increase in population while providing more effective transport of equipment, ore and miners.
Several renowned mines in the district included the Blue Bell, Lelan-Dividend and the Iron King mines.
Although worked in the 1880s, the first major production at the Iron King Mine occurred in 1906 and 1907, when 1,253 ounces of gold, 35,491 ounces of silver and 3,933 pounds of copper were mined there.
Over the next several decades the mine was developed with a two-compartment shaft extending below the 1,200-foot level.
Mining activity halted until World War I when George Colvocoresses mined sulfide ores for his smelter a mile east at Humboldt. Another period of inactivity followed from the 1920s into the mid-1930s. By the late 1940s, a 500-ton daily flotation mill was established at the site. The most productive period for the Iron King Mine occurred during World War II and the postwar period. In 1959 the mine was the largest lead and zinc producer in Arizona, at 3 million tons.
The town of Humboldt was founded in 1905 and named for 18th-century German scientist and explorer Alexander Von Humboldt. Humboldt declared the region, then known as Pimeria Alta, a vast treasure of wealth.
Several years later, its population increased to 1,000, with four general stores, eight saloons, a railroad depot, a movie theater, several hotels and an ice cream parlor and ice plant.
The Humboldt smelter was instrumental in processing the ores found in the district. Although the original smelter was destroyed by fire in 1904, it was rebuilt two years later. The 800-ton capacity Humboldt smelter processed copper and lead ores from the Iron King Mine, the Silver Belt Mine, Little Jessie Mine, Lelan-Dividend Mine, Crown King Mine and Blue Bell and De Soto mines.
Owned by Southwest Metals Co., the smelter closed in 1937 and the remaining mines in operation were directed to send their ores to the smelters at Clarkdale, Superior and Hayden.
Humboldt saw a temporary revival with the development of low-grade lead ores at the Iron King Mine by Prescott mining engineer Fred Gibbs in 1936, and with the Shattuck-Denn Mining Co. in 1942.
A cyanide-processing plant was built the following decade to treat the mill tailings from the 225-ton mill.
By 1968, the Iron King ore body was exhausted and its 250 employees were laid off. However, it had produced more than $100 million in lead and zinc.
After the Iron King Mine closed in 1968, all the underground equipment was removed and the mill was disassembled and auctioned. By the 1970s, the Ironite Products Co. bought the property using the tailings along with a combination of water, urea and sulfuric acid to create a product known as Ironite, used as fertilizer.
The Iron King Mine and Humboldt smelter are now a Superfund site with the U.S. Environmental Protection Agency involved in a feasibility study for site cleanup.