The urbanization of America changed, well, everything. Processed food was necessary for cities, because a lot of apartments & boarding houses didn't have much in the way of kitchens or food storage to encourage from-scratch cooking. This pushed farming technology to be able to keep up with the demands of cities. I believe there's also a link between people moving from farm to city, particularly after WWI, and the eventual design and building of our freeways. Not only did urbanites find after a while that they loved seeing the country rather than trudging through it, but freeways made large-scale livestock transport practical.
I respect the sheer courage it takes to specialize your diet these days--locovores, organic-only, vegetarian, vegan, whatever. Unless you had a medical reason a hundred years ago, you ate what you could unless you were wealthy. The thing that makes me grit my teeth and refuse to talk to people sometimes is when someone insists their dietary choice is right for everyone; I have a hard time keeping my big mouth shut on that one.
I kinda wish they'd print these things out like the old cereal-box Star Wars movies collector cards (we have a box my sweetie cut out of cereal boxes when he was 9). It'd be nice to have something to throw at aggressively optimistic foodies while I'm shopping for the imported citrus fruits because yeah, I like it local, yeah, I like farm-raised, but for (unladylike word here)'s sake I live at an elevation of around 4400 feet (not meters) above sea level and I don't want scurvy.
Also, it's nice to imagine dumping piles of these on unrealistic celebrity foodies.
