Thomas Jefferson had a bit of an obsession. He wasn't just looking for some dirt and trees when he sent his private secretary, Meriwether Lewis, into the abyss of the American West. He was looking for a water route—the legendary Northwest Passage—that would link the Atlantic to the Pacific. He thought he’d find woolly mammoths too. Seriously. He told Lewis to keep an eye out for prehistoric megafauna because he believed nature didn't allow species to go extinct.
The Lewis and Clark expedition officially kicked off in May 1804. It wasn't just two guys in a canoe. It was a military operation known as the Corps of Discovery. They started in St. Louis with about 45 men, a massive keelboat, and two smaller pirogues. Most people picture a peaceful stroll through the woods. It wasn't. It was grueling, dirty, and remarkably dangerous.
Why the Lewis and Clark Expedition actually happened
Basically, the United States had just bought 828,000 square miles from France in the Louisiana Purchase. Napoleon needed cash for his wars, and Jefferson was happy to take the land for about $15 million. The problem? Nobody knew what was actually there. Maps of the time showed the Rocky Mountains as a thin, easily crossable ridge. They thought you could just hop over a small hill and see the Pacific Ocean.
They were wrong.
Lewis and William Clark weren't just explorers; they were early-1800s data scientists. They were tasked with recording everything. Jefferson wanted weather patterns, soil quality, and detailed descriptions of every plant and animal. If you look at Lewis’s journals, they are packed with sketches of salmon, eulachon (candlefish), and the grizzly bear. Before this journey, science didn’t even have a formal name for the grizzly. Lewis described it as "a most tremendous looking animal" that was incredibly hard to kill. One bear took eight lead balls to the chest and kept charging.
The myth of the lone scout
You’ve heard of Sacagawea. You’ve seen her on the gold dollar coin. But the way she’s often taught in schools—as a "guide" leading the men through a trackless wilderness—isn't quite right. She was a teenager, a Shoshone woman who had been kidnapped by the Hidatsa and sold to a French-Canadian fur trapper named Toussaint Charbonneau.
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When the Lewis and Clark expedition hired Charbonneau as a translator, they got Sacagawea as a package deal. She was carrying her infant son, Jean Baptiste, on her back. Her real value wasn't just knowing the trail; it was her presence. A group of forty armed men looks like a war party. A group of forty men with a woman and a baby looks like a family or a peaceful trade mission. She was a "white flag" of peace.
Also, she was a linguistic bridge. When they finally met the Shoshone to buy horses—which they desperately needed to cross the mountains—Sacagawea realized the chief, Cameahwait, was actually her brother. It’s one of the few moments in the journals where the stoic military tone breaks and shows real emotion. Without those horses, they likely would have died in the snow.
Life on the trail was actually pretty gross
They ate a lot. I mean, an incredible amount of meat. When game was plentiful, each man consumed about nine pounds of meat a day. They hunted elk, deer, and bison. When they ran out of that? They ate dogs. They bought dogs from local tribes because they were desperate for protein. Clark couldn't bring himself to do it at first, but Lewis grew to prefer dog meat to elk, which he found lean and "tasteless."
Disease was a constant threat.
Lewis acted as the doctor. He brought a medicine chest filled with "Rush’s Thunderbolts," which were powerful laxatives containing high levels of mercury. If you had a headache, Lewis gave you a mercury pill. If you had a fever, you got a mercury pill. Modern archaeologists can actually track where the Lewis and Clark expedition camped by testing the soil for mercury deposits in the latrine pits.
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- Total distance: Around 8,000 miles round trip.
- Deaths: Only one. Sergeant Charles Floyd died near present-day Sioux City, Iowa, likely from a ruptured appendix. Even in a modern hospital in 1804, he wouldn't have survived.
- Total new species: 122 animals and 178 plants described for science.
Crossing the Bitterroots
If you want to talk about the hardest part of the trip, it’s the Bitterroot Mountains in Idaho. This was September 1805. The men were starving. The mountains were covered in snow. There were no animals to hunt. They were reduced to eating "portable soup"—a sort of dried, gelatinous broth Jefferson had commissioned in Philadelphia. It tasted terrible. Everyone was weak, dehydrated, and suffering from dysentery.
They finally stumbled out of the mountains and met the Nez Perce. The tribe could have easily wiped them out and taken their rifles. Instead, they fed them dried salmon and camas roots. It saved the expedition. It’s a recurring theme: the Lewis and Clark expedition succeeded not just because of rugged individualism, but because of the hospitality and geopolitical interests of the Indigenous nations they encountered.
The Pacific and the long walk back
They reached the Pacific Ocean in November 1805. They built Fort Clatsop in present-day Oregon to survive the winter. It rained almost every single day. Their clothes rotted off their backs. They spent most of their time making salt from the ocean and sewing elk-skin clothes to replace their wool uniforms.
The vote they took to decide where to camp for the winter is a big deal in history books. Why? Because York, an enslaved man owned by Clark, and Sacagawea were both allowed to vote. It was a rare moment of egalitarianism in an era where neither would have had a voice in "civilized" society.
The return journey in 1806 was much faster. They knew the way. They split up to explore more territory—Lewis took a northern route, Clark took the Yellowstone River. They finally rolled back into St. Louis in September. People had assumed they were long dead. They were celebrities for a moment, but the aftermath was messy.
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What happened next?
History isn't always kind. Meriwether Lewis was appointed Governor of Upper Louisiana, but he struggled with the bureaucracy and his own mental health. In 1809, just three years after returning, he died of gunshot wounds at an inn called Grinder’s Stand on the Natchez Trace. Most historians believe it was suicide, though his family long maintained he was murdered.
William Clark fared better. He became a successful politician and served as Superintendent of Indian Affairs. He also raised Sacagawea’s son, Jean Baptiste, paying for his education in St. Louis.
York’s story is the most tragic. Despite his vital contributions—he worked as hard as any man in the Corps—Clark refused to grant him his freedom upon their return. York eventually gained his freedom years later, but he struggled to find his footing in a world that didn't care about his status as an explorer.
Visiting the trail today
If you want to see what the Lewis and Clark expedition saw, you can't just look at a map. You have to go to places like the White Cliffs of the Missouri in Montana. It looks almost exactly as it did in 1805. You can float down the river and see the same sandstone formations Lewis described as looking like "elegant ranges of lofty freestone buildings."
For a real sense of the hardship, visit Lemhi Pass on the border of Montana and Idaho. This is where Lewis hiked to the top of the ridge, expecting to see a plain leading to the ocean, only to see "immense ranges of high mountains still to the West of us." It was the moment he realized the Northwest Passage was a myth.
Actionable insights for your own exploration
- Read the original journals: Don't just read summaries. The University of Nebraska has the journals online. They are raw, mis-spelled, and fascinating.
- Visit the Interpretive Centers: The one in Great Falls, Montana, is arguably the best. It focuses on the portage of the falls, which took the men weeks of grueling labor.
- Check the Lewis and Clark National Historic Trail: It’s not a hiking trail in the traditional sense. It’s a series of sites stretching across 16 states. You can drive most of it.
- Respect Tribal Lands: Much of the trail passes through sovereign Indigenous nations. If you’re visiting, research the specific history of the Mandan, Hidatsa, Arikara, and Nez Perce people from their own perspectives.
- Pack for the "Bitterroots": If you go hiking in these areas, remember that weather changes in seconds. Even in late summer, snow is possible.
The expedition changed the map of the world. It was a feat of navigation and survival that remains mind-blowing today. But it was also the beginning of a massive shift that would eventually lead to the displacement of the very people who helped Lewis and Clark survive. Understanding both sides of that history is the only way to really get the full picture.