The 14 Duty-to-Retreat States
Feel free to share the list below, I don't claim any ownership of it, I merely made the effort to build it. That said, if you'd care to cite www.lawofselfdefense.com as the source, that would be greatly appreciated!
15 14 Duty to Retreat States (as of 6/17/18):
Wyoming (became SYG effective July 1, 2018)
That's the list. That said, don't forget my default advice:
Anyone who actually HAS a safe avenue of retreat and doesn't take advantage of it, rather than go hands on, is an idiot. The moment you go hands on, you've immediately incurred a greater than zero risk of death and a greater than zero risk of going to jail for the rest of your life. There ought to be few circumstances that justify taking on such risks if you could simply safely retreat instead.
Also, keep in mind that in most of the 36 "stand-your-ground" states, there is no legal duty to retreat before acting in self-defense, but the prosecutor can still argue to the jury that they can consider whether the defendant could have safely retreated in evaluating whether the defender's use of force was reasonable. A half-dozen states are "hard" stand-your-ground states in retreat is taken completely off the table and such an argument by the prosecutor is not permitted, but they are in the minority.