Many found their fortunes, many more did not. but some say the greatest legacy of California's rush for gold was in the toxins and environmental damage left in its wake -- a legacy that still hasn't been fully examined to this day.
At first, the fortune-hunters who came to California mined with their hands, panning for sparkling gold nuggets in pristine waterways.
Then they built giant dredgers and put them in rivers and streams, or fired huge water cannons, pummeling hillsides to expose the gold beneath the surface.
And they mined underground, in thousands of miles of shafts created with explosives, discarding millions of tons of shattered stone.
"The Gold Rush left behind toxic materials, which to this day, threaten the water of the people of California," said Elizabeth Martin from the Sierra Fund.
Martin is executive director of the Sierra Fund, a Nevada City-based environmental group studying what it calls the "toxic legacy" of the California Gold Rush.
"The primary thing we're concerned about is mercury, which was left behind by the miners. Millions of pounds of mercury are in our environment here," said Martin.
During the Gold Rush, miners used mercury to extract the precious metal from quartz and stone.
Carrie Monohan is a hydrologist and science director for the Sierra Fund. She pulled mercury from Nevada City's Deer Creek using a turkey baster.
"Elemental mercury attached to sediment is what we're measuring. But then mercury gets mentholated, It becomes biologically available and accumulates in the food chain," said Monohan.
In some streams in Nevada County, recent tests done by the United States Geological Survey found levels of mercury in fish that exceed safe standards for human consumption as determined by the Environmental Protection Agency.
California has issued a warning to fisherman not to eat their catch in some areas, but not everyone heeds those warnings.
A study done by California State University at Chico found mercury from contaminated fish can accumulate in the human body, causing damage to the brain, nerves and immune system.
Dr. Roger Hicks is director of a Grass Valley health clinic. He thinks studies of mercury as a potential cause for developmental delays, retardation and other health problems he sees in local communities are long overdue.
"There's a saying in medicine. You'll never find a fever if you don't take a temperature," said Dr. Hicks. "My concern is with chronic mercury poisoning, which is a little bit, everyday, over time."
It took just a short time to leave the massive environmental scars still seen at Malakoff Diggins, north of Nevada City. In the late 1800's, it was the site of the world's largest hydraulic gold mining operation.
When Malakoff Diggins was in full operation, they had eight giant cannons shooting 100,000 gallons per minute of water onto the hillsides in the Sierra Foothills, 24 hours per day.
In 30 years, 41 million cubic yards of earth had been excavated at Malakoff, leaving an open pit over a mile in length and as much as 600 feet deep.
Tracy Gidel was the Hazardous Materials Program Manager for Nevada County for 15 years. Besides mercury, he worries about other toxic materials stirred up and left behind by miners in places like Malakoff.
"I think there needs to be a serious increase in the efforts to educate the public about the mercury, the arsenic, the lead -- all of it," said Gidel.
But there are those who say there's just not enough scientific evidence that the Gold Rush was all that bad.
Michael Miller is the president of the 16 to 1 mine in Alleghany. The Sierra Fund has no issue with the modern-day practices of the 16 to 1, which it considers environmentally sound.
But Miller takes issue with Sierra Fund claims that the California Gold Rush was one big environmental disaster.
"The Gold Rush period is a very short period," said Miller. "There's no way they could have done the decimation of the Sierra Nevada, as is alleged."
Miller points to the experiences of those whose families have lived in the area since the Gold Rush -- people like Bill Gassaway.
"We've all eaten the fish out of the streams around here, and played with the gold, played with the mercury and a lot of our elder people around here are sharp as a rock," said Gassaway.
The Sierra Fund is seeking millions of dollars in public and private funds to conduct further study, including health screenings. They hope their efforts lead to extensive environmental cleanup of the Sierra Gold Country.
Wednesday at 11 pm, in another Assignment 7 report from the Sierra, ABC7's Laura Anthony shows us the excitement around what many are calling the "new" gold rush.
That's thanks to the high price gold, which is at record levels, topping out at more than a $1,000 an ounce earlier this year.
The Sierra Fund
409 Spring St.
Nevada City, CA 95959
State Historic Park
23579 North Bloomfield Rd.
Nevada City, CA 95959
State Historic Park
Grass Valley, CA
Original Sixteen to One Mine