 <unk> George Grimes and Moses <unk> were the first to discover gold in the forest at the eponymous Grimes Creek on August 2 , 1862 . Subsequent gold discoveries at Rocky Bar in 1863 and Atlanta in 1864 increased the rush of people to Idaho , and in 1863 Idaho City , with a population of 6 @,@ 267 , surpassed Portland , Oregon as the largest city in the Pacific Northwest . The Idaho gold rush was largely over by 1870 , and the population of the Boise Basin fell from 16 @,@ 000 to 3 @,@ 500 . In 1898 the forest 's first gold dredge was built in <unk> and followed by several others . By 1951 when the last dredges shut down , at least 2 @.@ 3 million ounces ( 65 @.@ 2 million grams ) of gold had been produced from the Boise Basin area . Silver was mined along the Crooked River from 1882 until 1921 , but a silver mine at Silver Mountain proved unsuccessful . Following a shortage of mercury during World War II , mines in the <unk> area became the country 's largest producer of tungsten and second largest source of mercury . The most important known <unk> deposit of niobium and tantalum in the United States is located in Bear Valley . From 1953 until 1959 dredges there produced $ 12 @.@ 5 million ( $ 101 million today ) in niobium , tantalum , and uranium . Other minerals mined in the forest include antimony and <unk> . 
