[InterceptPoint]

Gibbs is probably the greatest American-born scientist of all time.

Better than Feynman?

[AndyJackson]

Better than Feynman?

Nope.

[RightWingAtheist]

Feynman is close, but he would still face stiff competition from Joseph Henry, as well as from Millikan, Compton, Lawrence, Wheeler and Alvarez when evaluating the great American scientists of the past century. And from Murray Gell-Man too, of course.