The significance of the Gold Rush for westward expansion in the United States was profound, as it accelerated the migration and settlement of the American West. Beginning in 1848, when gold was discovered in California, thousands of prospectors, known as "49ers," flooded into the region, seeking fortune and new opportunity. This massive influx of settlers spurred the development of towns, infrastructure, and the establishment of a more robust economy in the West. The Gold Rush also contributed to debates over slavery, increased tensions with Native Americans, and ultimately played a key role in the United States' territorial expansion and the concept of Manifest Destiny.