When gold was discovered near Sutters Mill, California in 1848, it brought a huge influx of people to the area, at first those already living in California and the surrounding areas, but when the story broke in the East Coast newspapers, from all over the world. San Francisco, the nearest port, became a Boom Town.
They became known as "'49ers" from the year when the biggest crop of would-be miners arrived. At first, finding gold was easy, and the miners prospered. But as the most obvious sites played out, mining required more and better skilled effort, and competition grew for the best claims.
By 1855, only large mining companies were still viable, and the Rush was over. Most of the Forty-Niners went on to other professions in the newly-booming states; a few stubbornly stayed in the prospecting business, moving from site to site in hopes of striking it rich elsewhere.