Bro Zito shared this with me recently straight out of the AMA magazine March 2014 issue. Apparently for an extra $20 it could be legal to vertically mount your license plate soon in the great state of Pennsylvania. Hopefully more states are already on this.
The plan is to have the state cons stamp and print the letters and numbers sideways so it reads correctly when mounted. Not sure if and when it will happen but if it is something you are into keep an eye on the google machine for news. It is called PA House Bill 1060.
At the bottom of the Bill there is an attached memoranda with details of this that you can read about right HERE.