The Argo Gold Mine and Mill is a former gold mining and milling property in Idaho Springs, Colorado, featuring an intact gold mill built at the entrance of the Argo Tunnel. The tunnel was built between 1893 and 1910 to drain the gold mines in Virginia Canyon, Gilpin Gulch, Russell Gulch, Quartz Hill, Nevadaville and Central City and allow easier ore removal. The success of the tunnel as an access route meant that a large volume of ore began exiting at the Idaho Springs entrance and a large mill was built to process it. At the time it was one of the largest such tunnels and milling operations in the world, directly recovering nearly $100 million in gold (11.2 million ounces) valued in 2023 at $10.1 trillion. They also sent another $200 million of high-value ores to smelters in Denver.
The property was closed in January 1943 after a major hydraulic accident in the tunnel, and never reopened after a federal moratorium was placed on gold mining during World War II. In 1976 it was purchased by a local investment group led by James N. Maxwell, who wanted to preserve an example of the Colorado gold rush mines. It was renovated and reopened as a tourist attraction and mining museum, and presently continues to offer daily tours. It was added to the National Register of Historic Places in January 1978.
The Argo Mill is open all year for tours, weather permitting. Visitors are provided with a brief history movie, an ore sample and mining equipment demonstration, a tour of the now-reopened tunnel entrance, and a descending tour of the mill structure and extant equipment including gravity separators, amalgamation trays, and froth flotation cells. An indoor museum on the bottom level includes many mining artifacts. An outdoor museum, partly visible from the street, includes larger period equipment used in various stages of extraction, separation, and smelting. A gold panning experience is provided to tour visitors. The outdoor museum and gold panning can also be experienced as a stand-alone attraction.
The Argo Gold Mill and Argo Tunnel in Idaho Springs, Colorado made quite an impact on the state’s mining history. It all began in 1859 with the first discovery of placer gold, and continued until 1943 following a fatal underground accident that closed the mill and tunnel forever. The best way to learn about this significant time in Colorado’s past is to visit the Argo Gold Mill and Mine, now a national historic site. Renovated and opened to the public in 1978 as an educational tour, most of the original equipment used for processing the ore remains in place, albeit a bit worse for the wear.
A visit to the Argo also includes a self-guided tour of the Double Eagle gold mine, and a chance to pan for gold. The main attraction here is not a mine tour, but rather a mill tour with a history lesson thrown in. The bottom level of the mill serves as a museum displaying mining tools, milling artifacts, and old photographs. A custom-built 1930s trommel, a funky spiral concentrator, ore cars, stamp mills, and even a miner’s porta potty are scattered around the property. Take a close look at these relics—you’ll likely gain a new appreciation for modern-day mining methods and equipment!
Tours kick off with a presentation by a member of the Argo staff. You’ll not only learn the history of the Argo Mill and the Argo Tunnel, but also the difference between placer mining and hard rock mining, and how and why it all got started on this spot back over a century ago. During the talk, samples of gold and gems found in the local mines are passed around the room. A film is also shown that helps bring the Argo’s story to life, as does a very loud pneumatic drill demonstration.
Following the demo, a short bus ride up the hill to the 1890 Double Eagle gold mine (on the same level as the top of the five-story mill) begins the self-guided portion of your tour. At the top, you’re on your own to explore a short section of mine, and then to walk back down through the mill. Inside the mill, you’ll encounter narrow stairs with uneven treads, loose floorboards, and shaky handrails, so watch your step and your children. Interpretive signs rather than a tour guide help explain how the mill and much of its machinery once operated.
The Argo’s story began with the discovery of gold in Idaho Springs, at the confluence of what is now Chicago Creek and Clear Creek. George Jackson was responsible for this first major find in 1859, which set off Colorado’s Gold Rush. Good news traveled fast, and practically overnight 50,000 gold-seekers streamed into Clear Creek Canyon.
After a couple of decades, the easy placer gold in the streams gave out and lode mining replaced panning and sluicing. At least 100 hard rock mines— the Orr, Queen, Sunnyside, Bertha, Arizona, Saratoga and many, many more— were worked between Idaho Springs and Central City, a distance of a little more than four miles. As the shafts were sunk ever deeper into Quartz Hill and the Seaton and Pewabic Mountains, the mines filled with water. As the mines reached depths of 500 and 1,000 feet, pumping costs made up the bulk of the mining expense, and soon enough, mines that could have continued to produce were closed. Prospectors just couldn’t stay ahead of the rising water or the rising costs.
The solution to the water problem was to build a tunnel that would run horizontally below the vertical mine shafts. The tunnel would not only act as a drainage system, but also provide ventilation and transportation of the ore to a processing mill. Last year (2013) was the 120th birthday of the Argo Tunnel, initially known as the Newhouse Tunnel. The project was started in 1893 thanks to Samuel Newhouse and his investors, and was the most ambitious and costly mining venture ever undertaken at the time. But it proved worth the risk.
Drilling and construction continued for 17 years, and by 1910 the Argo Tunnel ran from the east end of Idaho Springs to the northwest corner of Central City. Along the 4.16-mile route, it intersected directly or by crosscut tunnels to an estimated 100 mines. The tunnel was built on a slight grade to allow water to flow in a flume out to the portal. The first two and a half miles of the tunnel was 12 feet wide with a double track. Beyond that, the width of the tunnel decreased to 10 feet allowing for a single track. The combined benefits of drainage without pumping and the ability to haul ore to a mill at the tunnel’s portal allowed mines that had been closed for years to reopen.
In 1913, soon after the Argo Tunnel was in operation, the Argo Mill was completed. The most up-to-date milling processes were incorporated here to ensure the highest percentage of precious metals recovery. During its three-decade lifetime, the mill processed over 100 million dollars of gold ore! Electric locomotives were used to haul three-ton ore cars to the mill. Each mine that shipped ore to the Argo Mill through the tunnel was allocated a separate storage bin. Upon arrival, the ore was assayed to determine its mineral content. If both the mine owner and the mill agreed on the value, the total ore shipment was sold to the mill and concentration began.
On your slef-guided tour down through the mill, you’ll see many pieces of machinery that were used to extract gold and other minerals such as silver, copper and lead from the rock. The diversity of the local ore required many different types of equipment. One example is an amalgamation table. Amalgamation is the process of removing gold by absorbing it in mercury while other metals and waste rock wash away. The gold and mercury mixture (amalgam) was heated, causing the mercury to vaporize and leave nearly pure gold behind. Flotation cells were another major concentrating method used in the Argo Mill. Finely ground ore was combined in a complicated chemical/water/oil/air mixture. Metallic particles then floated to the top and formed a froth. This gold-bearing froth was skimmed off and dried.
At one point, seven concentrating tables were in use at the Argo. The vibration of this type of table caused powdered ore to separate into bands of heavy and light materials as it washed across wooden ridges. Heavy gold could be removed in this way and further concentrated by amalgamation, flotation or cyanidation. Today, one of the mill’s old cyanide leaching tanks serves as a photo gallery, which is located in the museum on the bottom level of the mill. You can actually walk into the round tank and admire an interesting collection of black and white photos of early local mining activities. Just try not to think about all those caustic chemicals of yesteryear!
Several varieties of ore-crushing and grinding machines were also at work at the Argo. The arrastra, ball mill, and tube mill functioned to break up the ore and expose the individual particles of valuable metals so they could be separated from the waste rock. Twenty 1,050-pound stamps were also used to pulverize gold-bearing ore. No amount of earplugs could block out the deafening noise of a stamp mill!
Operations at the Argo Mill and Tunnel continued quite successfully until a fatal accident occurred on January 19, 1943. Four miners working in the tunnel blasted into a water-filled shaft (pumping had stopped and the unused area had not drained), causing a huge wave to flood out the tunnel entrance, instantly drowning the four men. For hours, the water blasted out of the tunnel like a fire hose. Coincidentally, it wasn’t long after the accident that the federal government ordered all gold mines in the United States to shut down because they were not seen as essential to the war effort. The Argo Tunnel and Argo Mill closed forever.
Throughout the ages, hard rock miners have contended with many of the same problems: water drainage, ventilation, and economic transportation of their gold bearing ore to a processing mill. Fortunately, these problems were resolved for the area miners for a good amount of time, allowing for many to truly strike it rich. The diggin's around Idaho Springs yielded millions of dollars of gold— and that was when the shiny stuff was only worth $18 to $35 per ounce. Eureka!
The Argo Tunnel is a 4.16-mile (6.69 km) mine drainage and access tunnel with its portal at Idaho Springs, Colorado, USA. It was originally called the Newhouse Tunnel after its primary investor, Salt Lake City mining magnate Samuel Newhouse, and appears by that name in many industry publications from the time period when it was constructed. The tunnel intersected nearly all the major gold mines between Idaho Springs and Central City and is the longest such drainage tunnel in the Central City-Idaho Springs mining district.
The mines along the Argo Tunnel are no longer active or maintained but continue to exfiltrate ground water. The drainage from the tunnel was a major source of pollution in Clear Creek, until the U.S. Environmental Protection Agency (EPA) began treating it with a facility, built near the tunnel entrance. Large drainage tunnels in other mining districts include the Sutro Tinnel on the Comstock Lode in Nevada, and the Leadville Tunnel and the Yak Tunnel at Leadville, Colorado.
The associated gold ore mill is open to public tours. As of 2017, the tunnel's front portal was re-opened to the public and included on the tour circuit.
The Argo Tunnel was started from its southern terminus at Idaho Springs in September 1893, and reached its final length of 4.16 miles (6.69 km) in November 1910, after several pauses in the work. The actual time spent driving the tunnel was nine years and seven months. The tunnel intersected nearly all the major mines between Idaho Springs and Central City.
The tunnel was built on an incline of one-half percent, so that water from the intersected mine workings would drain out the entrance at Idaho Springs rather than needing to be pumped out. In addition, loaded ore cars from the mines could benefit from gravity as they were trammed downhill to the tunnel entrance and then returned uphill as empties. Previously, ore from the mines was hoisted out of the vertical shafts and trucked to railroad sidings or mills. The tunnel was driven in a north-northwest direction, perpendicular to the predominant orientation of the gold veins. It was hoped that the tunnel would intersect previously undiscovered gold veins, but there is no record that important new ore bodies were discovered.
The tunnel operated until January 1943, when miners attempting to construct access and drainage for the Kansas Lode mine group near Nevadaville critically weakened a wall between the Argo and a flooded mine works. The section was holding back water at a later-estimated pressure of 500 psi (approximately 1,155 feet of hydraulic head), and a large slug of water was ejected through the tunnel and out the entrance, killing the four miners at the blasting site. A fifth person near the portal suspected trouble when the lights suddenly failed and ran for the entrance, narrowly escaping. Water was ejected for several hours.
Due to preparations for World War II, the federal government ordered all gold mines in the US to shut down shortly before the accident occurred, intending that the workers and mining resources should be available for metals considered more essential to the war effort. The Argo Tunnel never reopened.
The Argo Tunnel continued to drain acid water from the mines and was recognized as a major continuing source of dissolved metals in Clear Creek. In May 1980, a surge of water flowed from the tunnel and turned the water in Clear Creek orange for some distance downstream. The temporary large increase in flow was attributed to a roof collapse somewhere within the tunnel damming a large volume of water behind it, then failing suddenly.
The U.S. Environmental Protection Agency listed the tunnel as part of the Central City/Clear Creek federal Superfund site in 1983, and built a treatment system at the mouth to neutralize and remove heavy metals from the 700-US-gallon (2,600 L) per minute acid mine drainage flow from the Argo, as well as lesser flows diverted to the plant from three other nearby mineworks, before it flows into Clear Creek. The treatment system began operation in 1998. The water treatment plant is just west of the old ore mill. A later modification to the tunnel included a high-pressure bulkhead installed roughly 200 feet inside of the portal entrance, enabling flow variations to be buffered inside the tunnel.
In January of 1859, George Andrew Jackson discovered gold in Clear Creek, and John Gregory found gold in the North Fork of the same river on May 6. Jackson’s discovery led to the creation of modern-day Idaho Springs, and out of Gregory’s discovery emerged Central City, Black Hawk, and Nevadaville. Nevadaville has since become a ghost town, but Idaho Springs remains home to approximately 2,000 people. Central City and Black Hawk, although less populated, now primarily serve as gambling towns. The Argo Tunnel, whose construction began in 1891 and finished in 1910, served to connect the two mining areas and provide drainage for the water used in mining operations. At about $5 million dollars to build and just under 22,000 feet long, the Argo Tunnel was the longest tunnel in the world in 1910. The effects of the Argo tunnel are still noticeable in both tourism and the efforts to clean up the Clear Creek area.
Mining took place in Idaho Springs from 1859 to the early-1940s, when gold mining halted due to World War II. Meanwhile, the Central City–Black Hawk area quickly lost mining importance in the 1880s, and in 1918 the area stopped producing gold, pivoting to emphasize tourism through the Central City Opera House. However, by the 1980s, Central City and Black Hawk faced significant structural and health issues. The water had been condemned, and the city could not financially provide upkeep for historic buildings. In response, Colorado voters brought gambling back to the area. Once known as “the richest square mile on earth,” Central City has since taken a backseat to Black Hawk, although both still retain own casino districts. Due to the reintroduction of gambling, Black Hawk and Central City became concerned with cleaning up the pollution from and remnants of mines.
Meanwhile, because of Idaho Springs’ proximity to Interstate 70—convenient for commuting to Denver—the old Argo Mill and Argo Tunnel are visible from the freeway. The tunnel was sealed on January 19, 1943 when an accident flooded the chamber and killed four individuals. In addition to draining water from mines by using a low-grade decline from its origin in Central City to the end point in Idaho Springs, the Argo Tunnel also served to ventilate the mines and provide ore transportation.
In total, the Argo Tunnel processed around three trillion dollars’ worth of gold by today’s standard. Today, visitors can view original mining equipment, the Argo mill itself, and part of the Argo Tunnel. The tunnel is not safe due to the buildup of mining pollution, but removing the pollution is currently part of the EPA superfund site’s goals. Individuals can even experience a glimpse of the lives of Jackson and Gregory as they pan for gold. Overall, the Argo Tunnel serves as a reminder of the environmental damage caused by decades of mining as well as the town histories of Central City, Black Hawk, and Idaho Springs.
Argo Gold Mine & Mill is a national historic site located about 45 minutes from Denver. Year-round tours are led by experienced guides and cover the tunnel, the mine, and the mill. There is a live demonstration of crushing, milling, and rock drilling.
It began in 1893 with the construction of the Argo Tunnel. After 17 years it reached Central City, about 4.5 miles away. The tunnel provided a way of transporting the gold from many mines along the way.
Argo’s Mill was constructed to process the gold-bearing ore being transported from the mines. When it was completed, the Argo Mill was the world’s largest mill of its kind. It processed over 100 million dollars of gold ore at prices of $18 to $35 per ounce.
Tours last about an hour, so wear comfortable shoes and bring a light jacket. Afterward, the tour everyone on the tour gets to try their hand at gold panning. Keep any gems you find. You can also buy miners’ bags of dirt, with guaranteed placer gold and gemstones.
The Argo Mill and Tunnel
Soon after 1859, when Colorado’s first gold was struck in Idaho Springs, CO, the Argo and surrounding area became an international center of milling and tunneling innovation and served for many gold mines in Colorado. Partnerships between local entrepreneurs, highly skilled professionals, and international business leaders enabled projects of previously unforeseen scale, ambition, and productivity to be realized. The Mighty Argo has rekindled this spirit and will resume its role as a hub of activity and an engine of economic productivity for the region and beyond.
The Argo Mill and Tunnel is a wonder of ingenuity, technology, and entrepreneurial spirit. Begun in 1893, the 4.2-mile-long Argo Tunnel cuts an ingenious path through the hills, draining and servicing hundreds of miles of workings, thereby prolonging the productivity of the famous gold mines in Colorado for decades. Many of the gold mines in Colorado would have become inoperable if not for the Mighty Argo. A vast amount of the Mill’s original equipment is still in place, transporting visitors instantly back in time to an era steeped in the Victorian Industrial Revolution of the American West. The Argo is also part of a 400 square mile EPA Superfund Site. The property has been remediated and hosts over 40,000 visitors annually.
IDAHO SPRINGS, Colo. (CBS4)- The Argo Tunnel and Mill has been the focal point of Idaho Springs for more than 100 years and its new owners want to not only preserve it, but develop some of the land around it.
"This is truly a national treasure that people don't know about," said Mary Jane Loevlie, one of the facility's owners.
For years, the Argo has been offering tours. Patrons can explore the tunnel and mill and pan for gold like miners did in the 1800s. But, at 124 years old, the Argo is starting to show its age.
"We've got windows that are falling out, metal sheets that are falling off. There are little pieces here we need to worry about, "said Loevlie.
Loevlie grew up in Idaho Springs and is part of a group of locals who bought the facility, along with Denver developer Dana Crawford. Just this year they received a grant from The History Colorado State Historical Fund.
The mine is expected to get $15,000 which they will use to address structural issues to make sure tourists are safe. What will happen to the Argo after that is ambitious to say the least. Loevlie says they have big plans for the area.
"This valley needs a hotel, it desperately needs housing, and we need to showcase forever the iconic nature of this mill," Loevlie told CBS4's Dominic Garcia.
In their vision plan the hotel will have a conference center and adventure cabins. There will also be housing units, a greenway bike path, even a brewery/restaurant.
The hope is to preserve the old west charm of the Argo but give people even more reasons to pull off Interstate 70 for a visit… something the majority of people who drive by aren't doing right now.
"I'd almost say 80 percent of the people that come here have always seen this red building on their way by. We call them whizz-bys."
Mary Jane knows how special the Argo is, and wants all those whizz-bys to see it too.