The Gold Rush era refers to a period in the mid-19th century when large numbers of people flocked to areas where gold was discovered, particularly in the United States. The most famous event was the California Gold Rush of 1849, which began when gold was found at Sutter's Mill. This discovery led to a massive influx of prospectors, known as "forty-niners," seeking wealth and opportunity. The Gold Rush significantly impacted the economy and population of the regions involved. Towns sprang up rapidly, and many became boomtowns, while others faded away once the gold was depleted. The era also contributed to the expansion of infrastructure, including roads and railroads, and played a role in the westward expansion of the United States.