Rock Oven (replica)
Fort Clatsop Historic Park
J. Agee photo
Properly speaking, a cairn, is a mound of rocks erected as a memorial or marker. The so-called "Salt Cairn" pictured here represents a reasonable guess as to the appearanceof the oven the salt makers built.
Among the "objects worthy of notice" President Jefferson instructed Meriwether Lewis to watch for en route were saltpetre deposits, salines, "& such circumstances as may indicate their character." Saltpetre, or nitre (potassium nitrate) is white and tastes salty, but is not a substitute for sodium chloride. It was mixed with charcoal and sulfur to make gunpowder. The I.E. DuPont de Nemours Corporation was founded at Wilmington, Delaware, in 1802 to manufacture high grade powder, but it was not in full production until 1804, so the best gunpowder Lewis could buy was imported from Europe.
By "salines" Jefferson meant salt flats, salt marshes, salt pans, salt springs, and rock or "fossil" salt deposits. Most would contain a variety of salts, including sodium chloride, which was an extremely valuable resource for a nation whose citizens already were moving westward. The explorers made firsthand observations, and collected secondhand reports of salines such as the Salt River (now Salt Creek), a tributary of the Platte River in Nebraska.
There was one objective not listed by Jefferson in his instructions to Lewis, but believed by many people then, and even mentioned in the official description of the Louisiana Territory. That was the supposed existence, about a thousand miles up the Missouri River, of a mountain of rock salt 180 miles long and 45 wide. On that matter the expedition's diarists were mute.
They did, however, observe that the Shoshones were the first Indians they had met who would taste salt. "These Indians all appear very fond of salt," wrote Private Whitehouse,"and eat it with their meat &ca. This we judged from some Captain Lewis gave them." The officers had previously given salt to Indian chiefs, but we don't know if the gift was appreciated or not. Most Indians on the Plains as well as to the east rarely used it. In the West, tradition suggests that the Tillamooks and other Indians south of the Columbia may have used it, but the Chinooks to the north did not.
Virgil J. Vogel, American Indian Medicine (Norman: University of Oklahoma Press, 1963).
Alfred L. Kroeber, "Salt, Dogs, Tobacco," Anthropological Records, Vol. 6, No. 1 (Berkeley, University of California Press, 1941).