Christopher Latham Sholes designed the QWERTY keyboard layout in 1878. Sholes had been working on a typewriter design since the late 1860s, but 1878 is the first documented appearance of the QWERTY design.
No one is entirely sure why Sholes chose to lay out his keyboard in the way he did, with several of the more popular letters, including E, N, R and T, not on the "home spaces" at the center of the keyboard. One theory is that he wanted to avoid jams by keeping common letter pairings, such as "th" or "he" separated. Yet, "e" and "r," one of the most common pairings, are right next to one another. Even with the move to electronic typing, the QWERTY layout has remained popular, likely due to the difficulty of learning a new system once one has been learned.