"As the spring and summer of 1848 advanced, the reports came faster and faster from the gold-mines at Sutter's sawmill. Stories reached us of fabulous discoveries, and spread throughout the land. Everybody was talking of "Gold! gold!!" until it assumed the character of a fever. Some of our soldiers began to desert; citizens were fitting out trains of wagons and pack-mules to go to the mines. We heard of men earning fifty, five hundred, and thousands of dollars per day..." - William Tecumseh Sherman

One of the most important and memorable events of the United States' westward push across the frontier came with the discovery of gold in the lands that became California in January, 1848. Located thousands of miles away from the country's power centers on the east coast at the time, the announcement came a month before the Mexican-American War had ended, and among the very few Americans that were near the region at the time, many of them were Army soldiers who were participating in the war and garrisoned there. San Francisco was still best known for being a Spanish military and missionary outpost during the colonial era, and only a few hundred called it home. Mexico's independence, and its possession of those lands, had come only a generation earlier.

Everything changed almost literally overnight. While the Mexican-American War technically concluded with a treaty in February 1948, the announcement brought an influx of an estimated 90,000 "Forty-Niners" to the region in 1849, hailing from other parts of America and even as far away as Asia. All told, an estimated 300,000 people would come to California over the next few years.