Before inventors figured out how to ship iceberg lettuce across the continent, people subsisted on root vegetables for most of the year.
Lettuce was the first fresh produce that Americans were able to buy any day or week of the year. Prior to this, they relied on root vegetables like cabbage, potatoes, and carrots. Lettuce exploded onto the culinary scene when growers in California's Salinas Valley figured out how to send train cars filled with iceberg lettuce across the continent to diners in New York City, Boston, and Chicago. Iceberg has the unique ability to stay crisp and fresh if its ambient temperature is maintained at 32 degrees Fahrenheit (0 C). It has a long shelf life of 21-26 days, fourteen of which were needed to reach Chicago at the time. The Salinas Valley also had access to electricity to power ice-making plants, where 30,000 pounds of ice were produced daily to fill the rail cars, below and above the lettuces.
By the 1950s iceberg lettuce was the most commonly consumed lettuce in the U.S., with average per capita consumption around 20 pounds. Refrigeration technology developed to the point that iceberg lettuce was even shipped to American soldiers in Vietnam.
But then, the iceberg growers and packers, who were always looking to improve their business model, realized that not all heads of lettuce got fully eaten because they were only ever sold in a full-head form. That led to the next revolutionary invention -- that of bagged salad greens.
Jim Lug, who worked to design the first bags, says that there are numerous layers within the plastic that you cannot see. One layer is to seal the bag, another allows for oxygen transmission, another provides a layer for printing graphics, and one is for carbon dioxide management -- all this within the see-through packaging of salad mix.
Their invention, however, meant that farmers could now ship more fragile lettuces, like Romaine, arugula, endive, Boston bibb, butterhead, and radicchio, further afield. As a result, mixed salad greens, or mesclun mixes, became a normal part of the American diet.
Photo credit: Dwight Sipler via Flickr, Creative Commons license.