The prevalent QWERTY key layout was implemented in the first economically successful typewriters, because that configuration tended to prevent the mechanical typebars from jamming as they converged near the typewriter ribbon. Dvorak recognized the QWERTY layout had a number of inherent flaws.

Excerpt from Wired.com.

I didn't know before that there is actually a different keyboard layout other than QWERTY and QWERTZ. This Dvorak's layout is really blowing my mind, tempting me to test one if I had a chance.