Missouri River Breaks: Geological Observations by John W. Jengo
The Citadel-Rock on the Upper Missouri
Engraved by Charles Vogel after Karl Bodmer c. 1837 (altered)
Assume for a moment that you are a mid-19th-century geologist planning to survey north central Montana between the Missouri Breaks and the White Cliffs. The Corps of Discovery made its way up this stretch of the Missouri River during the last week of May, 1805, and you would find the journals a good start for understanding its geology . . . . As a professional geologist and a Lewis and Clark enthusiast I have come to know this country well and am impressed by what the captains had to say about it, as suggested by the following journal excerpts and commentary.
—John W. Jengo