The title of Mad Men episode 7.13 is The Milk and Honey Route. A “milk and honey route” is “hobo code” (yep) for an easy railroad line with plenty of food along the way. This academic paper (pdf) points out that a route may vary in its plenty by individual hobo.
The original milk and honey route was a railroad from Salt Lake City southward through the valleys of Utah. Along this line were the Mormon villages so euphoniously named, Moroni, Manti, Nephi, Lehi and Juab. In the early days, before the Latter Day Saints got disillusioned by the great influx of bums and yeggs, or, what is worse, the auto tramps, this was the greatest feeding ground for hobos. Hence the name, milk and honey route, which has since become a household term among hobos. Any railroad running through a valley of plenty may be called a milk and honey line.
By the way, this paper is from Fairfield University, which is where Betty studied psychology.