When gold was discovered at Sutter’s Mill in CA, pack trains soon became indispensable in hauling supplies from the port at San Francisco to the gold fields on the western Sierra slopes. By 1852, more than 16,000 mules, valued at more than $800,000, were concentrated in the northern counties. About 1,800 mules operated out of Shasta alone.
By 1855, the California mule population swelled to over 31,000. A “Pack-Mule Express” transported gold from mines to banks.