Other trends and inventions had also helped make it possible for Americans to very their daily diets.Growing urban populations created demand that encourage fruit and vegetable farmers to raise more product.Railroad refrigerator cars enabled growers and meat packers to ship perishable great distances and to preserve them for longer periods. Thus ,by the 1980 s northern city dwellers could enjoy southern and western strawberries ,grapes, and tomatoes , previously available for a month at most for up to six months of the year.