Mercury Pills Marked Expedition Camps

During the 28-month Lewis and Clark Expedition that was launched from Camp Dubois, Missouri, on May 14, 1804, members used Dr. Rush's Bilious Pills, aka "thunderclappers," to treat constipation and other ailments. Each dose contained 10 grains of calomel, a mercury compound that acted as a powerful purgative. The travelers deposited the mercury in latrine pits, where it remained in the soil. Centuries later, researchers detected that mercury at Travelers' Rest near Missoula, Montana, helping them identify one of the more than 600 camps recorded in the expedition's journals.

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