The Lewis & Clark expedition has always been an interest to me (have wanted to pack up the camper and retrace their route, stopping off here and there and wetting a line where ever possible). I've read the log book/journals they kept of that incredible adventure and stand in awe of their accomplishments. There is a particular account of how much meat each member consumed each day on an average and occasionally there was mention of fish consumed, too. Makes you wonder just how the fishing was accomplished. Evidently they did not venture into where the national park is today but as the as the attached site says, they passed some 50 miles to the north. Also says one member of their party stayed behind for the return trip and says he (John Colter) was probably the first white man to see the wonders of the park during the winter of 1807-08. This all does not have much to do with who first fly fished the area but I can't help but think it's of some interest to whoever visits there.

http://www.nps.gov/yell/planyourvisi...ad/Yell273.pdf