According to Wikipedia, the California ghost town of Volcano was so-named because of the shape of the valley, which early miners erroneously thought was caused by a volcano.

I became interested in this former gold mining center as I was writing up the description of a Wells Fargo document in my collection.

Here is my description:

[Volcano, California] Wells, Fargo & Co. Express Receipt. San Francisco, California: Towne & Bacon Print. July 17, 1859. One page engraved express receipt.
For a shipment from Volcano, California of one sealed package valued at $1,500 and to be delivered to the banking department with the proceeds to be returned to Volcano. Today Volcano is a ghost town, but in the gold mining days it was a boom town. The town, in Amador County, California, is named for its setting in a bowl-shaped valley which early miners thought was caused by a volcano. The town dates back to the late 1850’s and was originally nicknamed “Crater City”. It is said that in 1849 one miner took out 8 thousand dollars’ worth of gold in a few days. Another got 28 pounds in a single pocket. In 1851 a post office was established and by April 1852 there were 300 houses, and by 1853 there were 11 stores, 6 hotels, 3 bakeries, and 3 saloons. Hydraulic operations began in 1855 and by 1867 most of the mining operations were idle. George A. Macomber, the consignor was a senior member of the firm of Macomber Bros. He came across the plains in 1850 with his brothers. For many years they operated mines in Tuolumne, Calaveras and Amador counties. In Amador County they practically established their right to be known as the fathers of hydraulic mining in California.

To me this document has so much going for it in terms of California local history: gold mining, shipments of gold via the iconic Wells Fargo Express, (does any one else think of a John Wayne film like War Wagon?) and of course, what is now a ghost town with the colorful, if erroneous name of Volcano. This is why I love researching these items to see the back story. Thanks to the interwires for making so much information easily available!