Lyric discussion by Stripeythecrab 

Cover art for Idaho lyrics by Gregory Alan Isakov

It seems to be about fond, perhaps also sad, memories of his past or childhood. Not sure who the "Mary" in the second chorus is - maybe a common friend with the addressee of the lyrics. No matter what the meaning, this is such a beautiful song! I love it!

My Interpretation

@Stripeythecrab I had the feeling that Mary was someone who had died. "down she goes"...