The Bizarre Way Scientists Confirmed a Lewis and Clark Campsite

Every kid who went to school in Montana knows the basics of the Lewis and Clark Expedition, so we can skip the textbook stuff. What’s interesting is that there’s actually very little physical evidence of where the Corps of Discovery camped in Montana.

Sure, we have the famous initials carved into Pompey’s Pillar. And thanks to the detailed journals kept by the expedition, historians have a pretty solid idea of where they traveled and when. But hard physical proof of their campsites? That’s surprisingly rare.

In fact, there’s only one archaeologically verified campsite from the Lewis and Clark Expedition in the entire country, and yes, it's in Montana.

The proof… was in the poop.

That site is Travelers’ Rest State Park, near the town of Lolo. Archaeologists confirmed the campsite in 2002 while excavating the area. According to Montana Fish, Wildlife & Parks, researchers uncovered several clues, including a trench latrine, fire hearths, and lead remnants from bullet-making.

But the real giveaway? Mercury. 

The mercury traces came from laxatives used by members of the expedition. According to the National Park Service, the Corps of Discovery ate enormous amounts of meat; sometimes up to nine pounds per person, per day. With essentially zero fiber in their diet, constipation was a predictable problem.

So before the journey began, Meriwether Lewis stocked up on about 600 pills of Dr. Benjamin Rush’s “Thunderbolts” Bilious Pills (also charmingly nicknamed Thunderclappers).

Like many medical “treatments” from the early 1800s, the pills contained a heavy dose of mercury. Not great for the human body, but extremely helpful for archaeologists, because mercury doesn’t biodegrade.

That chemical signature allowed researchers to match journal entries, maps, and historical guides used by the expedition, confirming that Travelers’ Rest was indeed the site where Lewis and Clark and their crew spent three days in September of 1805, resting before tackling the brutal crossing of the Bitterroot Mountains.

So yes, the only scientifically confirmed Lewis and Clark campsite in the United States was verified… thanks to 200-year-old laxatives.

About Travelers’ Rest State Park

Travelers’ Rest State Park sits along Lolo Creek on the edge of the town of Lolo and is open year-round. The visitor center operates from late April through early October, and the park hosts interpretive programs, demonstrations, and events throughout the summer. If you enjoy Montana history, it’s definitely worth the stop.