On Sunday morning, June 16, Lewis set out from his camp at the base of the first falls to rejoin Clark and the party at their camp, some six miles downstream. At 2:00 pm, the captains were reunited. Before they could discuss their problems, Clark informed Lewis that there was an even more urgent matter. Sacagawea was ill, and had been for almost a week. Clark had tried bleeding her, which hadn’t worked and applying to her pelvic region a poultice of Peruvian bark and laudanum, also without success. In his journal, Clark wrote, “The Indian woman verry bad, and will take no medisin what ever, untill her husband finding her out of her Senses, easily provailed on her to take medison, if She dies it will be the fault of her husband as I am now convinced” (He did not explain why he blamed Charbonneau).

Lewis’s initial cursory examination showed that Sacagawea was extremely ill, much reduced by her indisposition, with a high fever, a scarcely perceptible pulse, irregular breathing, and alarming twitching of the fingers and arms. “This gave me some concern,” Lewis wrote, for Sacagawea and her baby boy, of course, but even more “from the consideration of her being our only dependence for a friendly negociation with the Snake (Shoshone) Indians on whom we depend for horses to assist us in our portage from the Missouri to the columbia River.”

After giving her a fuller examination, Lewis concluded that “her disorder originated principally from an obstruction of the mensis in consequence of taking could.” Apparently he wasn’t far off in his diagnosis. His therapy was “two dozes of bark and opium,” which soon produced an improvement. She was thirsty. Lewis recalled a sulphur spring on the opposite (northwest) bank of the river and he sent a man to bring some of the water. She drank eagerly of the sulphur water, which was all the liquid Lewis would allow. He continued the application of the poultices to her pelvic region and by that evening was showing progress. Her pulse had become regular and fuller; a gentle perspiration had come on; the twitching had in a great measure abated, “and she feels much freer from pain.” He continued the medication-sulphur water and poultices-and allowed her to eat broiled buffalo and a soup of the same meat. With vast relief he wrote in his journal that evening, “I think therefore that there is every rational hope of her recovery,” an indication of how fearful he had been that she wouldn’t make it.

As the mountains began to close in, toward the evening on July 22, the expedition got a badly-needed morale booster. The men were laboring, often in the water pulling the canoes along, the river apparently having no end, the mountains crowding in, the great buffalo herds left behind on the plains and the days beginning to grow shorter. Sacagawea recognized this section of the river on which the Shoshones lived in the summer. The Three Forks were at no great distance ahead. “This piece of information had cheered the spirits of the party,” Lewis duly noted.