>>19464598You'd be amazed how deeply milk was tied to the history of the US, and to the individual home.
In the history of trains, you had the "milk runs", where dairies located away from town would ship their daily supply of milk, cream, butter, and cheese.
Within each town, you had home delivery of milk; and many homes (see image left), had a little door on the side of the house (usually at the garage) where the milkman would drop off your weekly, or whatever order.
I'm old enough to remember when school milk (see image right) came in glass bottles with little cardboard tops on them.
For more on the milkman, see:
https://www.youtube.com/watch?v=IgAh_UfQZHw 