Thirteen miles west of Thompson Falls and the banks of the Clark Fork River, a dirt road leads to a cluster of weathered green buildings and rusted remains of mining operations long quiet, until recently.
The humming comes from furnaces blasting pieces of slag into molten metal. This is Stibnite Hill, a smelting facility nestled in the Coeur D’Alene mountains. Inside, Plant Manager Rob Hill is in charge.
"This is what's called sodium antimonate. It's like wet sand. We run it with coal and soda ash into this furnace. It’s about 60 percent antimony."
Hill works for United States Antimony Corporation, or USAC. It’s a small company that has quietly operated here since 1969. Now, that’s changing.
Antimony is an ingredient used in certain military applications, including flame retardants, infrared sensors and nuclear weapons.
Antimony is an ingredient used in certain military applications, including flame retardants, infrared sensors and nuclear weapons. As the Trump administration’s policies to bolster domestic mineral extraction have rolled out, the lesser-known metalloid took center stage.
"We became literally the only game in town so we really had to start running," Hill says.
Stibnite Hill contains the only smelting facility for this material in the country. As a result, USAC was recently charged with replenishing domestic stockpiles. The project raises hopes and concerns for locals who have experienced the impacts of mining industries in western Montana.
For several decades, the U.S. has relied on foreign imports for antimony. Recent trade wars have compromised those imports.
In 2023, China, Russia and Tajikistan controlled about 90 percent of global antimony production. In December 2024, China banned all exports of it to the United States. That ban has since been lifted, but trade today remains stringent.
Last year, United States Antimony Corporation won a $248 million sole-source contract to resupply the federal government. CEO Gary Evans says they were the only company qualified to bid.
Last year, United States Antimony Corporation won a $248 million sole-source contract to resupply the federal government.
CEO Gary Evans says they were the only company qualified to bid.
"When the government needed more antimony ingots, which are used as an inventory supply for future wars, they contacted us."
The company grew significantly over the last three years. Their revenues more than doubled in 2025, as did their stock value. Most of that growth came prior to their first antimony deliveries to the federal government.
Montana Gov. Greg Gianforte attended the groundbreaking ceremony and issued a press release supporting the company’s growth.
"We've been able to basically take an older, sleepy company and revitalize it with a new board, new management team and new directions," Evans says.
The goal is to smelt 400 tons of antimony per month, ideally with ore mined from Montana, Idaho or Alaska. The expansion project cost $20 million and will add about 25 new jobs.
The goal is to smelt 400 tons of antimony per month, ideally with ore mined from Montana, Idaho or Alaska. To meet demands, the company must expand production capacity up to 500%.
The expansion project cost $20 million and will add about 25 new jobs.
One January morning, Plant Manager Rob Hill stands next to a cylindrical stone furnace, roaring with heat.
"What we need to do is get the antimony out of it," he says. "We just load it into there, heat it up, it melts down. We'll pour this whole thing up, this whole furnace will pour into these molds …"
In the next room, wooden pallets are stacked with dozens of shiny, grey antimony ingots.
"There’s over 100,000 pounds sitting here right now," Hill says.
Their primary role today is smelting, but officials say they plan to reopen the underground antimony mine here too. Company officials say some surface mining has already begun.
Just down the road, Kevin Bush owns the Wild Coyote Saloon, a restaurant, bar and campground. He says the uptick in activity has been good for business.
"I thought it was good, we needed jobs in this area, so yeah, I had no problems with it."
Inside the saloon, Plains-local Medric Jones sips a drink with his wife. He grew up a half hour from Thompson Falls and remembers mines supplying most of the jobs around.
"That's jobs for the people in the middle of nowhere. It's jobs for these people, us people," Jones says.
But the legacy of mining in the region also spurs concerns. Prospect Creek, a tributary of the Clark Fork River that runs adjacent to Stibnite Hill, is already on the state’s list of impaired waterways due to mining pollution.
Cesar Hernandez is with grassroots conservation organization, the Cabinet Resource Group.
"The organization I represent is not against mining, but if it has to be done it needs to be done right," Hernandez says.
He’s concerned about any mining projects approved under an era of weakened environmental protections and mining regulations.
"This isn't just an issue of jobs and big money, but there will be increasing impacts from whatever goes on up at the mine."
U.S. Antimony Corporation officials responded to these concerns saying they plan to “put the land back” in better shape than it was before.
Back in Thompson Falls, Robert Hill reflects on his 32 years with the company. He says the rapid growth has been impactful.
"This little backwoods Montana rural company is suddenly a hub of some very, very important materials, and we're a name and we are not used to that. We really aren't. It's a unique position to be in, for sure," Hill says.
The full expansion is estimated to be complete by the end of April. They plan to provide $75 million worth of antimony to the government in 2026.
Requests for interviews with local government officials about the project were denied.
