Gold was discovered on my land in 1848. i tried to keep this secret, but word got out and caused huge amounts of people to move west. who am i?

John Sutter. He was a Swiss immigrant who had a sawmill in California. His employee, James Marshall, was the first person to find gold on Sutter's land by accident. The two people determined it was really gold. Sutter wanted to keep it a secret, but the fact was soon disclosed by a journalist, so huge numbers of people (300.000, according to some estimations) rushed to California to mine for gold.