[Jedi Master Pikachu]

That could be one of the reasons why California has largest amount of illegal aliens. Grains (and apparently cotton) can be planted and harvested by machine. However, many (technically your "some" still works, but it is a lot) fruits and vegetables are still picked by hand (and California produces the most fruits and vegetables).

[TDA2]

You are exactly right. In Texas we have a some working in the farming arena but many more work in the feedlots, meat packing plants, etc. Any place that requires manual labor is where they will be. If you don’t have farming or the above then the number is greatly reduced.