More than a century ago, this wild stretch of mountain and rock was one of the richest mining areas on Earth.

Tons of zinc, silver and lead were extracted. Colorado's largest chunk of gold was found here, a 13-pound nugget named "Tom's Baby."

French Gulch is quiet now. Rusted rail cars and ore crushers rest in the shadow of the Rocky Mountains.

The mines are still producing, but it is a product no one wants.

Bright orange water runs from open shafts into tributaries of the Blue River, one of the state's major trout fisheries. Piles of waste rock, or mine tailings, stand 80 feet high and extend for 30 acres in all directions. Just beneath the surface, tunnels full of poisonous gas honeycomb the mountains, reaching under the nearby town of Breckenridge.

"Where do you begin here?" asked Russ Schnitzer, western field coordinator for Trout Unlimited, a group dedicated to protecting trout and salmon fisheries. "They tunneled through the mountain, took what they want and left the rest. It's a huge problem, the extent of which no one has a handle on."

There are as many as 500,000 abandoned mines nationwide, most of them in the West, government surveys report. About 100,000 of them are causing major pollution of rivers, streams and groundwater. Dangerous concentrations of mercury and cyanide along with heavy metals have killed off insects, fish and plant life in some areas. In others, contamination has threatened drinking water.

The Environmental Protection Agency says 16,000 miles, or 40 percent, of all Western headwater streams are now polluted by old, hard-rock mines, mines dug into solid rock.

With few government resources available, cleaning up the mess is difficult. The mine owners are either unknown or long dead. And those wishing to help fix the problem are often scared off by laws that would hold them responsible should they accidentally cause more pollution in their cleanup efforts.

"If you touch it, you own it," said Vern Schmitt, who works on mine issues for the U.S. Forest Service.

Rep. Mark Udall (D-Colo.) is pushing legislation that would limit the liability of those trying to restore polluted sites.

"There are a lot of good Samaritans that want to clean these up but won't touch them because of existing laws that make them liable," said Lawrence Pacheco, spokesman for Udall.

Money is also a problem.

Coal producers pay a 35-cent tax on every ton they excavate to help fund cleanup, but officials say that does not cover such an enormous problem.

When leaking mines are capped or plugged, limestone is sometimes spread around to absorb toxic runoff from the tailings.

Each site is intensely scrutinized before it is closed -- the mine's cultural history and the effect on bats living inside are considered, among other things. The cost of securing a mine can run into the millions of dollars.

"Everyone thinks when we close a hole it's easy, but it's much more complicated than that," said Mark Mesch, who heads Utah's abandoned-mine program. "It can take up to two years to do each one."

Mines, whether burrowed through alpine peaks or sunk into remote deserts, are testaments to the ruggedness of those who created them.

Using picks, shovels and dynamite, early miners tunneled through solid rock in search of mineral riches, altering the landscape as they dug.

"The history of the West was written in the mining camps," said Sam McGeorge, director of the National Mining Hall of Fame and Museum in Leadville, Colo. "Most people came out looking for gold in streams. They eventually went underground for silver, lead and copper. The reason the West is the way it is today is because people came out to dig for a better life."

According to the Western Governors Association, Arizona has the most abandoned mines, with 100,000; Nevada has 50,000; and Colorado is third with 22,000. Utah and California have about 20,000 each.

The mines are everywhere. Deep shafts pockmark mountainsides. Long chutes, huge mills and sagging smelters dot forests or sit along highways. The detritus of mining life -- old spikes, rusted cans of beans, knives -- often surround them.

For every ounce of gold or silver they claimed, miners removed tons of rock. These crushed and exposed tailings, often loaded with cadmium, arsenic and other potentially dangerous minerals, are piled high outside the mines. Rain and snow seep through the piles, carrying acids, phosphates and sulfides into rivers, where they kill fish and contaminate drinking water.

The Sacramento River in California has been badly contaminated by millions of tons of mercury, a byproduct of past gold mining activity. In Colorado, more than $155 million has been spent so far cleaning up the 1,400-acre Summitville Mine, according to the EPA.

"If no further action is taken, we will have a Western watershed devoid of trout," said Schnitzer, the fisheries coordinator, as his car went up a steep mountain road outside Breckenridge. "Trout are the canary in the coal mine. Where they exist, the water quality is good. But now we are seeing a lot of trout habitat adversely impacted."

At about 10,000 feet, a towering old mill emerged from the forest floor. The dark brown hulk, a remnant of the defunct Jesse Mine, stood 50 feet tall with many of its heavy beams holding firm more than a century after it was built.

Huge piles of tailings surrounded it. An abandoned mine shaft and tunnel are a short walk through the aspens.

Water, stained orange by iron sulfide, flowed from the shaft into a stream meandering toward the Blue River.

"There are thousands of places like this, and this one is small," Schnitzer said, staring into the soupy mixture. "It's just a huge problem. The history of the West is coming back to haunt us."