How were key positions on the typical QWERTY keyboard chosen? [closed]

Ironically, the QWERTY keyboard layout is designed to actually slow down typists so there would be fewer jams on the original mechanical typewriters. Newer layouts like DVORAK were designed to do the opposite but never caught on because people were too used to the QWERTY layout.

There is another story that says the top row contains all the letters in the word "typewriter" so salesmen could demonstrate it easily to customers.