Formed by the cataclysmic outburst flooding of Lake Bonneville during the Pleistocene ice age about 14,000 years ago, Shoshone Falls marks the historical upper limit of fish migration (including salmon) in the Snake River, and was an important fishing and trading place for Native Americans. The falls were documented by Europeans as early as the 1840s; despite the isolated location, it became a tourist attraction starting in the 1860s. At the beginning of the 20th century, part of the Snake River was diverted for irrigation of the Magic Valley. Now, the flows over the falls can be viewed seasonally based on snowfall, irrigation needs and hydroelectric demands. Irrigation and hydroelectric power stations built on the falls were major contributors to the early economic development of southern Idaho.