For such a striking phrase, it's a little ironic that I first came across it on this t-shirt design:
But then I started to hear the phrase everywhere. Loudon Wainwright III just put out an album by the same name and they interviewed him about it on NPR.
Finally, I came across the original source today from another Montanan's Flickr photostream. High, Wide and Handsome is the title of a history of Montana by Joseph Kinsey Howard, published in 1943. There's one copy at the Missoula Public Library, so I'm headed over there tomorrow at lunch to see what I can find.
I at least need to see more of Montana's high, wide and handsome side. It's calling for rain on Saturday, so I'm hoping to talk the MM into a scenic drive around the Pintler Loop to explore some new country. I'll let you know what we discover.