The breadbasket as the name implies, grows mostly cereal crops: wheat, corn, barely and not a cereal but diverse use: soy. There are small operations that do grow more traditional vegetables, but due to their labor intensive harvests and produces short shelf lives, they are not terribly profitable (without underpaid migrant workers located near large populations to consume or process the produce quickly). This in my opinion is why we see things like water intensive almonds, only being harvested in places like water scarce California. Labor cost is something vertical farms often treat as a given, which at least for most of our non-cereal produce production, it is not.

Absolutely cheap labour is a major component of the central valley's success. Also being able to run multiple seasons worth of crops.

That the rich and naturally irrigated soils of the midwest and northeast are basically only used for animal feed agriculture now is a real shame from an economic diversification and health POV but also from an environmental perspective. Giant swathes of topsoil are depleted every year, and fertilizer and pesticide runoff pollutes entire drainage basins of these regions.

Cash crop agriculture like this is highly capital intensive, so squeezes out smaller operators, and does very little to support the surrounding towns.