Charles Fritz did exactly 100 paintings of Lewis & Clark for a private collector with the condition that he never do another Lewis & Clark piece again after. This is one of the pieces. (Here is another.) All 100 works occasionally travel to museums, although I don't think it's on view now. A book was made if you're curious about the whole series. (Looking at the cover of the book, it appears this painting was an early version of the book cover or maybe Charles changed it. They're similar images.)