The most important event in the history of gold mining in the United States was the discovery of gold in California in 1848. It was previously known to exist in the country for rumors of it were current among the trappers, and placers had been worked in what is Los Angeles. The Padres of the neighboring mission of San Fernando had discouraged the business as demoralizing to their flocks and the existence of the precious metal was not widely known, still less was its distribution northward suspected.
In November, 1842 were sent 20 oz of California weight of placer gold to the U.S. Mint at Philadelphia. The mint assay was returned in August, 1843. The gold was taken from placers first discovered in March, 1842, by Francisco Lopez, a Californian, at San Francisquito, about 55 km north-west from Los Angeles. Lopez dug up some onions with his sheath knife and in the dirt discovered a piece of gold. A few persons, mostly Sonorians, worked these placers until the war with the United States disturbed the country. The discovery of gold in January, 1848 at Sutler’s saw mill on the southern fork of the American River, afterwards famous as Coloma, in El Dorado country was the beginning of the new epoch. This discovery was made by James Wilson Marshall, a partner in the mill, who observed in the debris washed down by the tail-race a glittering fragment of a mineral unknown by him. Suspected it to be gold, he sought for further specimens and obtained in the course of a few days several ounces of gold. Some tests made established its character and the news were spread rapidly arousing intense excitement in Europe.
In March, 1848, a San Francisco News Paper contained a paragraph giving the tidings. In May, the same publication announced the suspension of publication and the editors and workmen imitating their fellow citizens of every class went off to the diggings. Two years later, the population of California grew from 15,000 to 100,000 and the gold bearing zone extending along the west flank of the Sierra to Oregon was under active exploitation. The placers of the southern countries of Oregon were opened in 1852, those of the John Day and Powder Rivers in 1860. Gold was discovered in Idaho on the banks of the Peu d’Oreille River in 1852,but the active development of the territory dates from the discovery of the Oro Fino mines in 1860, and the opening 2 or 3 years later of the rich Boise Basin.
The first form of gold mining was digging. The miner loosened the auriferous soil with a pick and shoveled it into a pan, from which, by skill manipulation of water, the clay, sand and pebbles were removed and the heavier particles of gold left behind. The first improvement on the pan was the rocker, afterwards the tom was introduced and with it the sluice. In 1850 and 1851 the two latter devices began to be generally employed, in consequence of greater convenience of water supply afforded by the mining ditches. The first ditch of importance was made in 1850 and its success so stimulated imitation that in the course of eight years, 6000 miles of mining canals were constructed.