Why was the QWERTY keyboard developed?

Christopher Latham Scholes invented the qwerty keyboard in 1875.

It is a common misconception that the QWERTY keyboard was invented to make typing harder, in order to prevent expert typists from breaking the internals of the "Type-Writer" (as they were first marketed in the 19th century).

However, the reality is that common letter pairings are separated (such as TH, IE etc), in order to decrease the likelihood of a clash of the type bars in these early typewriters.

Other formats have been tried (AZERTY and Dvorak to name two) which each have their own benefits. In fact, the Dvorak format increases the number of Words which can be typed using just the home row (the row where your fingers naturally lay at rest, if you are a touch typist) to 400, from the approximate 100 Words which a standard QWERTY keyboard can produce.

However, in the 1950's independent tests showed that irrespective of the keyboard layout used, an expert touch typist will usually produce around 100 Words per minute.
Christopher Sholes was an American mechanical engineer, born on February 14, 1819 in Mooresburg, Pennsylvania, and died on February 17, 1890 in Milwaukee, Wisconsin. He invented the first practical modern typewriter in 1866, with the financial and technical support of his business partners Samuel Soule and Carlos Glidden. Five years, dozens of experiments, and two patents later, Sholes and his associates produced an improved model similar to today's typewriters. The Sholes typewriter had a type-bar system and the universal keyboard was the machine's novelty, however, the keys jammed easily.