President Thomas Jefferson instructed Meriwether Lewis, "Beginning at the mouth of the Missouri, you will take observations of latitude & longitude, at all remarkable points on the river, & especially at the mouths of rivers…." (DeVoto, 1953).  Thus, the journals of Lewis and Clark detail the confluence of the Missouri River with its tributaries.  The Cannonball, Little Missouri, and Yellowstone Rivers, which flow through North Dakota, are notable entries in the journals.

In addition to the confluences of the Missouri River and its tributaries, this site focuses on the Fort Mandan area, where Lewis and Clark spent the winter of 1804–1805; the Bismarck/Mandan area, from both historical and present–day perspectives; and the dams that have greatly affected the present-day Missouri River.

In North Dakota, the U.S. Geological Survey continues many of the scientific investigations begun by Lewis and Clark and the Corps of Discovery.  This web site gives a picture of the Missouri River and its tributaries during the early 1800’s, via excerpts from the journals of Lewis and Clark, and a picture of the present-day river system, via aerial photographs, U.S. Geological Survey data, and U.S. Geological Survey publications.  Because the production of maps was another endeavor common to the Corps of Discovery and the U.S. Geological Survey, the web site also provides a historical view of Missouri River and North Dakota maps from 1798 to the present.