Who would most likely have been a "forty-niner" during the California Gold Rush?

The answer is definitely gold seeker

Gold seekers hoping to strike rich. They left their homes. The largest group of forty niners however were Americans. The largest group continued to be Americans, but there were tens of thousands each of Mexicans, Chinese, Britons, Australians, French, and Latin Americans, together with many smaller groups of miners, such as African Americans, Filipinos, Basques and Turks.