My thru-hiking partner and I are going to kill each other over this issue! Please end it. I don't care who is right. Or at least give me a compelling argument for either side.
Where I am from we pronounce it app-a-lay-chin. In fact everyone I've talked to including some people who live with 20 miles of part of the trail in NY and PN pronounce it that way.
My friend however, lives in Boone N.C. and goes to Appalachian State College. I guess this instantly makes them the leading authority on naming the entire mountain range (in his mind at least). He pronounces it app-a-latch-in. In fact, thats how my name Latch has come to be. Because he is constantly sayng "Latch" to me when I'm talking about the trail.