Timeline of the Lewis and Clark Expedition

Timeline Lewis and Clark expedition

In the early 1800s one of the most influential explorations in United States history took place. The timeline of the Lewis and Clark expedition lasted just over twenty-eight months, but the planning for the journey began long before.

The Lewis and Clark expedition had many important discoveries that contributed greatly to the western scientific revolution. “Discoveries” of course, is relative as Native Americans had long known of the plants, animals, and topography that Lewis and Clark introduced to the western world.

The expedition, known as the Corps of Discovery, maintained well-detailed journals to help document exactly where and when the explorers reached certain milestones along the way.

Lewis and Clark’s expedition ultimately played an extremely significant role in helping the United States to map and explore the new territory from the important Louisiana Purchase.

Timeline of the Lewis and Clark Expedition

The timeline of the Lewis and Clark expedition can be broken into four distinct segments: 1803 and the preparations for the journey, 1804 and the expedition’s first year, 1805 when they reached the Pacific Ocean, and 1806 consisting of the return journey to St. Louis.

All along the way Lewis and Clark collected samples from the new territory, opened diplomatic relations with Native Americans, and mapped potential routes to the Pacific Ocean.

Their journey was widely publicized and historians credit the explorers with driving interest in westward settlement and the American concept of Manifest Destiny.

Lewis and Clark Expedition Timeline

1803: Preparations for the Journey

January 1803: President Jefferson sends a secret message to Congress asking for funds for an expedition to the Pacific Ocean.

April 1803: Diplomats James Monroe and Robert Livingston reach an agreement with France where Napoleon decides to sell the Louisiana Territory to the United States.

May 1803: Lewis Meriwether begins three weeks of training in Philadelphia to help during his upcoming journey. He studies botany, navigation, math, medicine, and anatomy.

June 1803: Lewis invites William Clark to co-lead the expedition. Clark responds a month later accepting the offer.

Lewis and Clark Expedition map
Map of Lewis and Clark expedition via Wikimedia

September 1803: After months of training and procuring supplies and equipment such as a massive 55-foot keelboat, Lewis writes his first entries in his journal. Lewis and Clark’s journals held a treasure trove of details about their journey that scholars still use today.1

October 1803: The US Senate formally ratifies the Louisiana Purchase treaty. Lewis joins Clark in Indiana and they spend the next two months recruiting men for the Corps of Discovery.

December 1803: Lewis and Clark split for the winter: Lewis in St. Louis, Missouri, and Clark at Camp River Dubois just north of the settlement. Lewis would procure more supplies during the winter while Clark trained the men to prepare them for the long journey.

1804: The First Year

March 1804: The men train and prepare during the winter for the rigorous journey ahead. Lewis and Clark attend ceremonies that formalize the transfer of the Louisiana territory to the United States.

May 1804: On May 14th the expedition begins with Clark leading the men north up the Missouri River to St. Charles. Lewis joins six days later. By the 25th the men pass through La Charette—the westernmost white settlement on the Missouri.2

June-July 1804: The group “discovers” new animals such as pelicans and encounters fur traders in the region. Mosquitoes and ticks plague the members, something they will constantly complain about.

Sacajawea statue Lewis and Clark
Statue of Sacajawea via LOC

Lewis and Clark operated the expedition under strict military standards. Court martials handed out severe punishments for disobedience such as 50-100 lashes and “running the gauntlet.”

August 1804: Lewis and Clark meet with Native American chiefs for the first time. They pass out peace medals and open diplomatic relations with the Oto and Missouri tribes, though the Chiefs were more interested in weapons than the medals.

“all Concluded by asking a little Powder & a Drop of Milk [whiskey]. I answered those Speeches gave them 50 balls one Canister of Powder & a Dram…”

The first and only member of the expedition dies from a likely burst appendix on the 20th.

September 1804: The expedition encounters the Lakota Sioux, one of the most powerful nations they will meet. By the 20th, the group crosses the Missouri River’s Big Bend.

October 1804: Lewis and Clark reach Mandan territory, a Native American nation in North Dakota that had close trading relations with the United States.

November 1804: The Corps hire Toussaint Charbonneau, a French fur trader living among the Mandan, as an interpreter. His Shoshone wife, Sacajawea, accompanies him. Construction of Fort Mandan begins as the group settles for the winter.

1805: Reaching the Pacific Ocean

February 1805: Sacajawea gives birth to Jean Baptiste Charbonnaeu, her first child with Toussaint. The infant stayed with Sacajawea the rest of the journey.

April 1805: On the 7th the Corps of Discovery emerge from their winter hibernation and resume their travels. Lewis sends roughly a dozen men back to St. Louis to deliver updates to President Jefferson as well as some of their discoveries, including a live prairie dog.

The remainder of the group consists of 31 men, including Clark’s black slave named York as well as Sacajawea and her infant.

May 1805: Sacajawea saves the priceless Lewis and Clark journals and other critical items after a storm capsizes one of their boats. Lewis sees the Rocky Mountains for the first time.

June-July 1805: The expedition reaches the Great Falls of the Missouri River. Over the next month they complete a grueling eighteen mile portage carrying thousands of pounds of equipment around the five waterfalls.

Depiction Fort Clatsop
Depiction of Fort Clatsop in the early 1900s via Wikimedia

August 1805: The expedition crosses the Continental Divide and encounters the Shoshone people. In a stroke of luck, the Shoshone Chief is Sacajawea’s brother, who lends the expedition horses, supplies, and a guide to help with the remainder of the journey.

By this time the expedition has traveled over 3,000 miles. Meanwhile, the Corps updates and cargo finally reaches President Jefferson back east in Washington, DC.

September 1805: The expedition nearly starves while traveling through the Bitterroot Mountains and resorted to eating some of their horses. The Nez Perce natives save the group by providing them food and shelter.

November 1805: Lewis and Clark finally spot the Pacific Ocean. The group votes on where to spend the winter. Every member, including the slave York and woman Sacajawea, has an equal vote. By December the expedition finishes construction on Fort Clatsop, named after the local Clatsop natives. 

1806: The Return Home & Aftermath

Winter 1806: The expedition experiences a cold, rainy winter that is typical of northern Oregon. In an April journal update one member of the Corps remarked:

“from the 4th of November to the 25th of March 1806, there were not more than twelve days in which it did not rain, and of these but six were clear”

March 1806: On the 23rd the expedition leaves Fort Clatsop after gifting the intact fort to the natives for helping them survive the winter. The expedition was desperate to return home, having run out of tobacco and whiskey, suffering from constant sickness and disease, and tired of the repetitive elk meat on which they survived.

May-June 1806: The Corps of Discovery once again reaches present-day Idaho and the Bitterroot Mountains, but realize that in their haste to return home, they left too early in the season. Snow still blankets the mountains, rendering them impassable.

Lewis and Clark fortunately find refuge and wait for the snow to melt with the Nez Perce natives. By June 24th, the expedition crosses the Bitterroots with three Nez Perce guides.

July 1806: The Corps of Discovery divides into two groups following the mountain crossing so as to explore as much territory as possible and attempt to find a better passage.

On July 25th, William Clark chisels his name and the date on a rock formation he names Pompeys Pillar, after Sacajawea’s son. His name is still visible to this day.

Pompey's Pillar William Clark
Clark’s signature on Pompeys Pillar via Wikimedia

August 1806: The expedition reunites together and continues on to the Mandan villages where they spent the winter of 1804-1805. Toussaint Charbonneau and Sacajawea remain with the Mandan, and Clark offers to care for and raise their son, promising opportunity and a western education.

With the Missouri River’s current in their favor, they travel upwards of seventy miles a day, making great haste.

September 1806: On September 23rd the expedition finally arrives in St. Louis, Missouri. The entire expedition took two years, six months, and ten days and consisted of nearly 8,000 miles round trip.


To recap, the timeline of Lewis and Clark’s expedition can be broken down across the four segments:

  1. 1803: Preparations for the Journey
  2. 1804: The First Year
  3. 1805: Reaching the Pacific Ocean
  4. 1806: The Return Home & Aftermath

The Lewis and Clark expedition was incredibly important for a variety of reasons, perhaps most significantly for its impact on American society over the following decades.

Nicholas Biddle later published a shortened and more concise version of Lewis and Clark’s journals for the general public. Their stories enthralled scores of people and helped lead to the concept of Manifest Destiny and the eventual push to expand westward across the continent.

Lewis and Clark became household names across the United States and gained fame for their feats. Both men earned high-ranking appointments in the aftermath: Lewis as Governor of the Louisiana territory, and Clark later as Governor of the Missouri territory.

Clark followed through on his promise to Charbonneau and Sacajawea by becoming the guardian of their child, Jean Baptiste, and seeing he received a formal western education.3

Interestingly, despite having immense freedom during the trip and even receiving an equal vote over the location of the 1805-06 winter lodging, Clark did not grant freedom to his slave, York, following the expedition.3

Clark fully expected York to resume his subservient role upon returning to American society, though York refused. Historians believe that Clark eventually sold York considering the slave became more trouble than he was worth.

The story is worth highlighting as it shows that no matter how valuable York was on the expedition, due to the color of his skin he was expected to be subservient to white men.

Slavery would continue to cause large divisions in American society over the subsequent decades.


To learn more about US history, check out this timeline of the history of the United States.


1) Thwaites, Reuben Gold. “The Story of Lewis and Clark’s Journals.” The Quarterly of the Oregon Historical Society, vol. 6, no. 1, 1905, pp. 26–53. JSTOR, http://www.jstor.org/stable/20609636.

2) Holmberg, James J., and Phyllis MacAdam. Into the Wilderness: The Lewis and Clark Expedition. University Press of Kentucky, 2003. JSTOR, http://www.jstor.org/stable/j.ctt2tv68m.

3) Soldier, Lydia Whirlwind. “Lewis and Clark Journey: The Renaming of a Nation.” Wicazo Sa Review, vol. 19, no. 1, 2004, pp. 131–43. JSTOR, http://www.jstor.org/stable/1409490.

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