Prior to the 1920s, most things people bought -- bread, fruits, vegetables -- were produced locally. People knew which butcher was good, and if they didn't like his stuff, they went to another one. But as trains got faster, people began to see products from far away. It was difficult to determine what product was best.
Brand names became really important. But since industrial farming was still in the future, you had tens of thousands of little farms -- each offering its own "brand" of vegetables. And to distinguish themselves, the brands had to come up with some really eye-catching ad campaigns
I love these old vegetable posters. They're inventive, often risqué, and aesthetically high-quality.