The most significant and longest lasting impact of the gold rush of the mid 1800s was

The discovery of gold nuggets in the Sacramento Valley in early 1848 sparked the Gold Rush, arguably one of the most significant events to shape American history during the first half of the 19th century. As news spread of the discovery, thousands of prospective gold miners traveled by sea or over land to San Francisco and the surrounding area; by the end of 1849, the non-native population of the California territory was some 100,000 (compared with the pre-1848 figure of less than 1,000). A total of $2 billion worth of precious metal was extracted from the area during the Gold Rush, which peaked in 1852.

On January 24, 1848, James Wilson Marshall, a carpenter originally from New Jersey, found flakes of gold in the American River at the base of the Sierra Nevada Mountains near Coloma, California. At the time, Marshall was working to build a water-powered sawmill owned by John Sutter, a German-born Swiss citizen and founder of a colony of Nueva Helvetia (New Switzerland). (The colony would later become the city of Sacramento.) As Marshall later recalled of his historic discovery: "It made my heart thump, for I was certain it was gold."

Though Marshall and Sutter tried to keep news of the discovery under wraps, word got out, and by mid-March at least one newspaper was reporting that large quantities of gold were being turned up at Sutter’s Mill. Though the initial reaction in San Francisco was disbelief, storekeeper Sam Brannan set off a frenzy when he paraded through town displaying a vial of gold obtained from Sutter’s Creek. By mid-June, some three-quarters of the male population of San Francisco had left town for the gold mines, and the number of miners in the area reached 4,000 by August.

As news spread of the fortunes being made in California, the first migrants to arrive were those from lands accessible by boat, such as Oregon, the Sandwich Islands (now Hawaii), Mexico, Chile, Peru and even China. Only later would the news reach the East Coast, where press reports were initially skeptical. Gold fever kicked off there in earnest, however, after December 1848, when President James K. Polk announced the positive results of a report made by Colonel Richard Mason, California’s military governor, in his inaugural address. As Polk wrote, "The accounts of abundance of gold are of such an extraordinary character as would scarcely command belief were they not corroborated by the authentic reports of officers in the public service."