Located along the Lewis and Clark River at the north end of the Clatsop Plains approximately 5 miles (8.0 km) southwest of Astoria, the fort was the last encampment of the Corps of Discovery, before embarking on their return trip east to St. Louis.

[3] The original Fort Clatsop decayed in the wet climate of the region but was reconstructed for the sesquicentennial in 1955 from sketches in the journals of William Clark.

The replica lasted for fifty years, but was severely damaged by fire in early October 2005, weeks before Fort Clatsop's bicentennial.

Jefferson set a number of goals for the expedition, most notably to determine what the land contained, including plants, animals, and natural resources.

In late November 1805, after spending a number of days in what is today the state of Washington, Lewis and Clark proposed that the Corps of Discovery move to a location along the Columbia River, based on a recommendation of the local Clatsop Indians.

The expedition overwhelmingly decided to take the advice of the local Indians to explore the idea of spending the winter on the southern shore of the River.

During Lewis' absence, the group performed a number of housekeeping tasks, including fixing their clothes from the wear they had suffered during the long and arduous journey.

All of the men lived in one structure, while Lewis, Clark, Sacagawea, her husband Toussaint Charbonneau, and their son, Jean Baptiste, stayed in the other.

Realizing the importance of their trip, Lewis spent most of his time at Fort Clatsop documenting the journey, taking notes on the wildlife, terrain, and other features.

Finally, Lewis and Clark occasionally traded with the Clatsop Indians, a tribe they had come to dislike, viewing them as untrustworthy and prone to theft.

The men were suffering from a number of different illnesses and conditions, including venereal diseases and respiratory problems, and felt that departing would make them all feel better.

Lewis decided not to send any of the men back with a copy of his notes by sea, as was usually customary, because of the small number of people in the group.

The location of the fort near the Pacific Ocean and the Columbia River made it a natural site for the fur trade, which expanded rapidly in the years after Lewis and Clark left.

A 9-1-1 operator's insistence that the fire was no more than fog over the nearby Lewis and Clark River delayed firefighters’ arrival by about 15 minutes, possibly impacting their ability to save part of the structure.