August 1, 1770 -
- William Clark, Born

August 18, 1774 -
- Meriwether Lewis, Born

March 6, 1801 -
- Lewis is asked by President Jefferson to be his secretary-aide

Spring, 1803 -
- Lewis picked as commander of expedition. Writes to ask William Clark to join him and share command. Clark accepts.

July 4, 1803 -
- Announcement of Louisiana Purchase.

Summer, 1803 -
- Large keelboat constructed in Pittsburgh, overseen by Lewis. After construction Lewis takes it down the Ohio River picking up Clark and recruits along the way.

Fall/Winter, 1803 -
- Camp Wood established upstream from St. Louis.

May 14, 1804 -
-Expedition begins.

July 4, 1804 -
-Expedition marks first 4th of July west of the Mississippi by firing the keelboat's cannon, and naming Independence Creek.

August 3, 1804 -
- Corps of Discovery meet with representatives of the Oto and Missouri Indians, give peace medals, 15 star flags and other gifts.

August 20, 1804 -
- Near present day Sioux City, Iowa, Sgt. Charles Floyd dies of a probable burst appendix. Captains name hilltops where he is buried Floyd's Bluff and a nearby stream, Floyd's River.

August 30, 1804 -
- Friendly council with Yankton Sioux held.

September 7, 1804 -
- All of the men attempt to drown a never-before-seen prarie dog out of its hole for shipment back to Jefferson.

September 25, 1804 -
- Confrontation with Teton Sioux, who demand one of the expedition's boats as a toll to travel farther upriver. Chief Black Buffalo resolves situation before any fighting. Expedition stays with tribe for 3 more days.

October 24, 1804 -
- Expedition discovers earthlodge villages of the Mandan and Hidatsas Indians. The captains decide to build Fort Mandan across the river from the main village.

November 4, 1804 -
- Toussaint Charbonneau, a French Canadian fur trapper living with the Hidatsas, is hired as an interpreter. His wife, Sacagawea, a Shoshone who had been captured by the Hidatsas and sold to Charbonneau, is also considered helpful as the Shoshones are said to live at the headwaters of the Missouri.

December 24, 1804 -
- Fort Mandan completed, expedition moves in for the winter.

February 11, 1805 -
- Sacagawea gives birth to baby boy, Jean Baptiste.

April 7, 1805 -
- Lewis and Clark send the keelboat and approx. a dozen men back downriver, with maps, reports, Indian artifacts and other scientific specimens for Jefferson. The remaining party heads west.

April 29, 1805 -
- Lewis and another hunter kill a large grizzly bear, which had never before been described for science.

May 29, 1805 -
- Clark names the Judith River in honor of a girl back in Virginia he hopes to marry.

June 2, 1805 -
-The expedition comes to a fork in the river. Lewis and Clark believe the south fork is the Missouri, while all of the other men believe it is the north fork. Although they are not convinced that the south fork is the Missouri the captains recount; "they were ready to follow us any where we thought proper to direct."

June 13, 1805 -
- Scouting ahead of the rest of the expedition, Lewis comes across the Great Falls of the Missouri. He also discovers four more waterfalls farther upstream. The expedition will have to portage over eighteen miles, taking nearly a month, to get past them.

Late July, 1805 -
- The expedition reaches the three forks of the Missouri River, and name them the Gallatin, the Madison, and the Jefferson, after the Secretary of the Treasury, Albert Gallatin, the Secretary of State, James Madison, and President Thomas Jefferson. The expedition continues southwest, up the Jefferson.

August 8, 1805 -
- Sacagawea recognizes Beaverhead Rock and says they are nearing the headwaters of the Missouri, and her people, the Shoshones. Lewis and three others scout ahead.

August 12, 1805 -
- The shipment sent from fort Mandan arrives in the East and is delivered to Jefferson. Lewis ascends the final ridge toward the Continental Divide expecting to see plains and a river flowing to the Pacific, but he finds even more mountains.

August 17, 1805 -
- Lewis discovers a village of Shoshones and tries to negotiate for horses. Clark and the rest of the expedition arrives as well, and it is discovered that the Shoshone chief Cameahwait is Sacagawea's brother. Lewis and Clark name the site Camp Fortunate.

August 31, 1805 -
- The expedition sets out with a Shoshone guide called Old Toby, along with 29 horses and a mule.

September 9, 1805 -
- The expedition camps at present day Missoula, Montana, a spot Lewis and Clark called Travelers Rest to prepare for the mountain crossing.

September 22, 1805 -
- After nearly starving in the mountains the expedition emerges near present-day Weippe, Idaho.

October 16, 1805 -
- The expedition reaches the Columbia River.

October 18, 1805 -
- Clark sees Mount Hood in the distance, named by a British sea captain in 1792, proof that they are near the ocean.

November 7, 1805 -
- Clark, who believes he can see the ocean writes his most famous journal entry: "Ocian in view! O! the joy." The expedition is actually still 20 miles from the sea. Terrible storms halt the expedition for nearly 3 weeks.

November 24, 1805 -
- By majority vote the expedition decides to cross to the south side of the Columbia River to build winter quarters.

January 4, 1806 -
- President Jefferson welcomes a delegation of Missouri, Oto, Arikara, and Yankton Sioux chiefs who had met with Lewis and Clark more than a year earlier.

March 7, 1806 -
- The expedition runs out of tobacco. They had run out of their whiskey ration the previous fourth of July.

March 23, 1806 -
- Fort Clatsop is presented to the Clatsop Indian, for which it was named, and the expedition begins the journey home.

May - Late June, 1806 -
- The expedition reaches the Bitterroot mountains, but must wait for the snow to melt before crossing them. During this time the expedition again stays with the Nez Perce, Lewis describes them as "the most hospitable, honest and sincere people that we have met with in our voyage."

July 3, 1806 -
- Having crossed the Bitterroots again, the expedition breaks into smaller groups in order to explore more of the Louisiana Territory. Clark and his group head down the Yellowstone River, while Lewis takes the shortcut to the Great Falls, and then heads north along the Maris River.

July 25, 1806 -
- Near present-day Billings, Montana, Clark names a sandstone outcropping Pompy's Tower, after sacagawea's son, nicknamed Little Pomp. On the rock face Clark enscribes his name and the date.

July 26-27, 1806 -
- While making their way back to the Missouri, Lewis' party encounters eight Blackfeet warriors. They camp together, but the morning of the 27th the party catches the blackfeet attempting to steal their horses and guns. During a fight two of the Blackfeet were killed.

August 12, 1806 -
- All of the parties are reunited downstream from the mouth of the Yellowstone River.

August 14, 1806 -
- The expedition returns to the Mandan village. Charbonneau, Sacagawea, and Jean Baptist stay, while John Colter is granted permission to return to the Yellowstone to trap beaver.

September, 1806 -
- With the current of the Missouri behind them, they are able to cover over 70 miles per day. The expedition also begins meeting boats of American traders heading upriver.

September 23, 1806 -
- Lewis and Clark reach St. Louis.

Fall, 1806 -
- Lewis and Clark are treated as national heroes. They return to Washington, D.C. The men receive double pay and 320 acres of land as reward, the captains get 1,600 acres. Lewis is named governor of the Louisiana Territory, Clark is made Indian agent for the West and brigadier general of the territory's militia.

October 11, 1809 -
- Lewis commits suicide at Grinders Stand, an inn south of Nashville.

December 20, 1812 -
- Sacagawea dies at Fort Manuel. Clark, who is St. Louis, assumes custody of Jean Baptiste, as well as her daughter, Lisette.

September 1, 1838 -
- William Clark dies at the home of his eldest son, Meriwether Lewis Clark. William Clark had married Julia "Judith" Hancock for whom he had named a river while on the expedition.