O'Brien, CA Photo - Fog obscures the exit from Lake Shasta Caverns, northeast of Redding, CA

Fog obscures the exit from Lake Shasta Caverns, northeast of Redding. The caverns are a network of caves located near the McCloud arm of Shasta Lake in California. It was formerly named Chalk Cave and Baird Cave; named after Spencer Fullerton Baird. The caverns, formed by flowing water, date back 200 million years. Over time, the water drained, leaving the caverns seen today. The caves are made entirely of limestone and feature every type of possible formation; including stalactites; stalagmites; soda straws; columns; and flowstone. The Discovery Room; one of eight known rooms in the cavern system; contains all types of limestone rock formation. The first recorded white explorer was James A. Richardson; a federal fisheries employee. His claim of discovery is still clearly legible on the wall where he wrote it that day â € “ November 11; 1878 â € “ with carbide from his miner's lamp. Until 1964; Lake Shasta Caverns were seen each year by only a handful of hardy spelunkers who inched their way through steep, restricted natural fissures to view its startling formations. Before opening to the public; a new entrance was needed; as the current was a small hole in the ceiling; barely large enough for one man to fit through. Using explosives; workers blasted a tunnel from a rock face deep into the mountain; hoping to reach the lowest known room: the Basement. However; along the way; a large rock wall was knocked down; revealing the Discovery Room; perhaps the most fascinating room in the caverns. As a result; the Basement Room ironically is not the lowest chamber. Today; the Lake Shasta Caverns attract thousands of visitors every year

Credit line: The Jon B. Lovelace Collection of California Photographs in Carol M. Highsmith's America Project, Library of Congress, Prints and Photographs Division.