Although founded in 1870, the first gold yield was reported in 1876. Over time, the operation expanded exponentially, with the towns of Sunny South and Bullion growing up around the two main tunnel entrances. In June 1910, a major cave-in forced the operation to close. However, Hidden Treasure lives on in history as the most productive drift mine in the state.
While the Hidden Treasure mine was discovered in 1870, its true history begins much earlier, roughly 50 million years ago.
An ancient system of rivers flowed through the area we now know as the Sierra Nevada. Eventually, the gravel riverbeds were buried within the developing mountains. These gold-bearing deposits are called channels and are often referred to as “white” if they are rich in quartz, or “blue” if they have unoxidized slate.
Early miners followed these channels but did not fully understand their origin.
By the 1850s, on a north-facing ridge ten miles from Iowa Hill, miners were prospecting these ancient channels. Overlooking the North Fork of the American River, these miners created the town of Damascus. The Mountain Gate Mining Company was the primary mining operation in the area; following a white channel of gold-bearing gravel.
While the exact science behind these gravel channels was still unknown, theories about glaciers or ancient rivers were common by the mid-1800s. These early theories were responsible for the founding of the Hidden Treasure Mine. It is purported that a miner and working owner of the Mountain Gate Mining Company, William Cameron, began to survey the surrounding area in 1870.
Cameron knew the mine in Damascus was utilizing gold-rich gravel channels, and he hypothesized that the channels ran further than the mine. On the southern slope of the opposing ridge, Cameron is reported to have made the initial discovery of the Hidden Treasure Mine in 1870, under the name “Cameron’s Mine.” However, it was abandoned that same year.
In 1875, Cameron returned with Michael Power, mining engineer and superintendent at Mountain Gate, to survey a new location for a successful placer mine. They blasted a new tunnel and ultimately reached a quartz-laden gravel deposit, known as a “white channel.” This was the exact type which was being profitably mined in Damascus. Cameron’s original theory had been true. The men formed a partnership and founded the Hidden Treasure, where the extraction of gold was first announced in 1876.
The mine was successful and a company town, Sunny South, grew quickly around the mine’s southern slope.
Miners, now working for wages, brought their families, expanding the town’s population. A white miner could earn $3.00 per day, while a Chinese worker earned $1.75 per day.
The operation required a large dump house to receive gravel from the mine, attached to sluices to wash and separate out gold. There was also a machine shop, blacksmith, forges, carpenter shop, mining office, bunk houses, storehouses, and stables.
The town had two hotels for miners and “well-furnished family cottages.” There were two general stores, a small school, and various forms of entertainment, including baseball and a band. The height of the population was about three hundred and fifty persons, with nearly fifty families.
Hidden Treasure was a drift mine, which was dug horizontally into the steep slopes to access the alluvial deposits of gold-bearing gravel.
The tunnel was supported by massive amounts of timber to brace the soft soil. It was reported that the tunnel used 85,000 support beams a year to secure the sides and ceiling. These timbers were as large as 14x14” square.
The extensive depth of the original tunnel from Sunny South, nearly two miles long, prompted the start of a new tunnel. In 1896, two miles above Sunny South, a new drift operation was started. Originally known as Centerville, and later Bullion, this town was the center of the Hidden Treasure Mine’s newest operation.
The main working tunnel from Bullion was dug to a depth of 4,500 feet, and steel rail lines were laid to accommodate wooden mine cars. A trolley wire line was installed to power a 28 horse-power electric mine locomotive.
The early mining operation required two, 12-hour shifts of seventy men to remove gravel with a pick-axe and shovel. Twenty-four hours a day, mule teams brought three hundred ore carts from the tunnel to the Mine Dump House to be sluiced and prospected. The dump house processed roughly 2100 tons (4.1 million pounds) of gravel a week.
Overtime, technological advancements increased production. A steam engine and steel track were installed, and a hydro-electric power station was built to provide electricity.
Despite continued success, a cave-in during the summer of 1910 effectively ended the operations of the Hidden Treasure Mining Company. One and a half miles from the main entrance at Bullion, the debris cut off access to the lucrative “white channel” of gold-bearing gravel.
The company’s stockholders refused to fund the cost of removing the cave-in debris or constructing a new tunnel.