Facts about Sulfur Spring

Over the River

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By the fifteenth of June, 1805, Lewis had made several trips along the far side of the river, and undoubtedly had noticed the strong, familiar odor as he passed the little pothole, for he named it "Sulpher spring." Chemists later would identify the odor as that of hydrogen sulfide, which is produced by the decay of anaerobic bacteria in standing water. "The spring," Lewis wrote that day,

is situated about 200 yards from the Missouri on the N.E. side, nearly opposite to the entrance of a large creek; it discharges itself into the Missouri over a precepice of rock about 25 feet, forming a pretty little cataract. The water is as transparent as possible, strongly impregnated with sulpher, and I suspect Iron also, as the colour of the hills and bluffs in the neighbourhood indicate the existence of that metal. The water to all appearance is precisely similar to that of Bowyer's spring in Virginia.

As can be seen in the chemical analysis of the water, there is no sulfur in Sulfur Spring. Sulfate (SO4) is an odorless and tasteless compound. But Lewis was right about the presence of iron in the soil thereabouts. There is enough oxidized iron in the water of Portage Creek that they also called it "Red Creek." In Sulfur Spring, however, there is only six one-hundredths of a milligram of iron, which is insufficient to impart more than a slightly alkaline taste.

The location of Bowyer's spring Lewis uses for comparison is unknown today, but "medicinal springs" were popular everywhere. Thomas Jefferson listed a few of them in his Notes on the State of Virginia, remarking that some of them were "indubitably efficacious, while others seem to owe their reputation as much to fancy and change of air and regimen, as to their real virtues." Openly skeptical of modern medicine, he pointed out that none of the waters had been subjected to chemical analysis, "nor been so far the subject of observations as to have produced a reduction into classes of the disorders which they relieve."1

Lewis should have said the spring was on the northwest side of the river, since at this point the Missouri is flowing generally northeast. The aerial view above is due westward. The fields on the prairie beyond the breaks are laid out along section lines, which always run north-south and east-west. The field above center is dark green with rising winter wheat. The light-brown fields are fallow; the dark brown ones have been freshly ploughed. Farmers' access lanes snake down the draws.

After the rest of the Corps arrived at the place Clark selected as the lower portage camp, on this side of the river (see photo), Lewis remarked that one of the small canoes was left below the rapid opposite the mouth of Portage Creek "in order to pass and repass the river for the purpose of hunting as well as to procure the water of the Sulpher spring, the virtues of which I now resolved to try on the Indian woman."


1. Thomas Jefferson, Notes on the State of Virginia, ed. William Peden (Chapel Hill: University of North Carolina Press, 1955), 34.

Funded in part by a grant from the Montana Cultural Trust.