That the columbia river.
Fort Clatsop was built in Oregon by the Lewis and Clark Expedition in 1805-1806 as their winter encampment. They chose this location near the mouth of the Columbia River to establish a base for exploring the Pacific Northwest. The fort provided shelter and protection from the harsh winter weather during their stay in the region.
Lewis and Clark finally arrived at the Pacific Ocean at Astoria, on the mouth of the Columbia River,
Lewis and Clark landed at the mouth of the Columbia River, Astoria, Oregon on November 7 1805.
they landed at the mouth of the columbia river
They split at the mouth of the Medicine River
That would be the mouth of the Columbia River at Astoria, Oregon.
Fort Clatsop was the encampment of the Lewis and Clark Expedition in the Oregon Country near the mouth of the Columbia River during the winter of 1805-06. Located along the Lewis and Clark River at the north end of the Clatsop Plains approximately 5 mi (8 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. The site is now protected as part of Lewis and Clark National and State Historical Parks. A replica of the fort was constructed for the sesquicentennial in 1955 and lasted for fifty years; it was severely damaged by fire in early October 2005, weeks before Fort Clatsop's bicentennial. A new replica, more rustic and rough-hewn, was built by about 700 volunteers in 2006; it opened with a dedication ceremony that took place on December 9th.For the source and more detailed information concerning your request, click on the related links section (Answers.com) indicated below.
high plain at the mouth of Knife River
It ended at the mouth of the Columbia River near Astoria, Oregon.
Oregon, near the mouth of the Columbia river.
The Clatsop people, a group of the Chinook Indians, are called Clatsop because the have traditionlly lived on the South side of the Columbia River near it's mouth at the present day Astoria, Oregon USA
They ended their expedition in Calvin, New York.