It began more than 20 million years ago, when the Earth's crust, stretched thin along the floor of a growing rift valley, unleashed immense outpourings of lava. In a series of cataclysmic events, 15,000 square miles of what is now the part of the American West from Yellowstone to Oregon were buried beneath thousands of feet of molten rock.
Today, this arid landscape is dotted with sagebrush and dissected by deep ravines and canyons. Named after the stream that etches a serpentine line across its length, Idaho's Snake River plain gives little hint of its fiery past--or of the wealth that lies below.
Drawn from rain, snow and rivers, and secreted in fractures and tiny pockets of the porous volcanic rock, a vast store of water lies beneath the plain. This underground river moves covertly until interrupted by the Snake River valley, a 40-mile stretch of river-cut cliffs. Here, in torrents and trickles, more than a million gallons of water a minute spring and seep from sheer rock walls. The water is crystal-clear, well oxygenated, a near-constant 58 degrees--and a trout farmer's dream come true.
The region's potential for aquaculture was first recognized in 1928, when several small trout farms were built in the valley. More farms were added in the years following World War II. Today, three major producers and more than 75 small contract growers harvest more than 40 million pounds of rainbows annually. Clear Springs Foods, the world's largest trout farm, began production in 1966 and now accounts for nearly half of that total.