New York Herald Reports on the Discovery of Gold in California

At the time gold was discovered, California was part of the Mexican territory of Alta California, which was ceded to the U.S. after the end of the Mexican-American War with the signing of the Treaty of Guadalupe Hidalgo on February 2, 1848.

On August 19, 1848, the New York Herald was the first major newspaper on the East Coast to report the discovery of gold. On December 5, 1848, President James Polk confirmed the discovery of gold in an address to Congress. Soon, waves of immigrants from around the world, later called the "forty-niners," invaded the Gold Country of California or "Mother Lode."

http://en.wikipedia.org/wiki/California_Gold_Rush