Stetson

The original hat designed by John B. Stetson was called "The Boss of the Plains," and it didn't actually look much like the iconic hat that we all think of.  But it was very popular, and the cowboys all bought it and took it out on the trail with them.

And as they wore it, and slept on it, and whacked cattle on the rump with it, the round domed brim tended to acquire a typical dent in the middle, from where the cowpokes grabbed it.  And the flat brim tended to curl up a bit, from being folded and stuck in saddlebags.  Newer cowboys wanted hats that looked like those that their older role models were wearing, so the design slowly shifted.  And so the iconic Stetson shape evolved-- not according to a milliner's design, but organically from the demands of the market.  Or something.  I could probably make some sort of really sappy metaphor about the democratic nature of the frontier and the will of the people and how it means Ron Paul should be president or something, but even I have my limits.

Hat Additional-- supposedly, the "Ten Gallon hat" (also a Stetson model) got its name not from its mythical capacity, but rather from the Spanish word galón, for the ten braids in the hatband.  This may be apocryphal, however.