montyb is correct about the keyboard's history.
I'm a righty, but prefer a computer mouse be on my left (although it still keeps the "right hand click" for when my husband uses it). I also am lefty with my coffee cup and a few other things.
As a high school student--back in the day of manual typewriters, discos, and the like--I was copy editor for our biweekly high school news page in our local paper as well as our school's monthly publication. While I was helping move furniture into the new library/media center, I wound up smashing the first 2 fingers on my right hand between two pieces of furniture, forcing me to wear a splint for a couple of months. By the time it was over, I was able to type with my left hand with nearly the same speed/accuracy as with two hands and without the hunt and peck method.
Right now, my 17 year old cat, Tigger, is laying on my left arm while I type this.