... we called the S.W. fork, that which we meant to ascend, Jefferson's River in honor of that illustrious personage Thomas Jefferson. [the author of our enterprize.] the Middle fork we called Madison's River in honor of James Madison, and the S.E. Fork we called Gallitin's River in honor of Albert Gallitin. ... the beds of all these streams are formed of smooth pebble and gravel, and their waters perfectly transparent; in short they are three noble streams.

Credit: Brent Phelps
http://afterimagegallery.com/phelps.htm