I've read a few anecdotes about professional magicians performing "in the field" for a number of different reasons: military and/or diplomatic. Perhaps the most famous is Robert-Houdin in Algeria, with productions and vanishes, implying French superiority in armaments and disappearing potential enemies.
I've just come across the story of an amateur performance, during the Lewis & Clark expedition, from April 2-3, 1806. There's Lewis with a noisy, sort of military demonstration with an air gun, and Clark, with a separate, somewhat more subtle demonstration of supernatural powers, featuring a fire show and compass-needle moving (would anyone mind asking Mr. Geller, at the Genii birthday bash, if he was inspired by Clark?). I read about the latter displays in "The Story of the Lewis and Clark Expedition," (Noah Brooks, Dover Books, New York, 2004, pp.258-259)
There's an account of the same incident in a free Google eBook, "The Men of the Lewis and Clark Expedition," (Clarke and Duncan, University of Nebraska, 2002, pp.252-253) here: http://books.google.com/books?id=xbHy-MxguHkC&lpg=PP1&pg=PA253#v=onepage&q&f=false
I'm wondering if anyone knows of any earlier documented "field magic" (either for the sake of entertainment or military/diplomatic) in North America. Thank you!