From the important cartographical library of Warren Heckrotte, a rare map covering northern California with details of the gold region.
The Sacramento Valley from the American River to Butte Creek. Derby accompanied Brigadier General Bennett Riley on a tour of the gold districts in the summer of 1849, and this map is the result. He arrived in California in June of 1849, at the height of the gold rush. During the next two years he undertook four field expeditions, including mapping the mining country and the lower Colorado River"