Why Americans love peanut butter.

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Feb. 9 2009 6:55 PM

Why Do Americans Love Peanut Butter?

They fell for it during World War II.

Peanut butter sandwiches.
Peanut butter and jelly sandwiches

Last week, Sen. Tom Harkin excoriated the company accused of knowingly supplying salmonella-tainted peanut butter to a free school lunch program, asking, "What's more sacred than peanut butter?" How did peanut butter become such a popular part of the American diet?

We can thank a vegetarian and a world war. Peanuts, which are cheap and high in protein, have been consumed in the United States for more than 250 years, but peanut butter wasn't developed until the 1890s and didn't become popular until the 1920s, when it was first mass produced. The meat shortage caused by World War II made the creamy spread an American icon. By the mid-20th century, peanuts had transformed from a slave food to a nuisance to a staple.

Peanuts were brought to the United States with African slaves in the 1700s and were sold roasted in-shell by street vendors as early as 1787. (Nineteenth-century ministers and theater owners complained bitterly of crackling shells and messy remains in their establishments.) During the Civil War, the invention of a mechanized harvester drove down the already-low production cost, and peanuts gained popularity among malnourished Southerners. Confederate soldiers used peanuts to make pies, a coffeelike beverage, and a chocolate substitute.

Confederates did not, however, make peanut butter. Although grinding peanuts into a paste seems a relatively obvious innovation, there is no clear reference to peanut butter in the United States until physician and vegetarian John Harvey Kellogg (who also co-invented breakfast cereal with his brother, Will Keith Kellogg) served nut butters to patients in his sanitarium in the 1890s. * Recognizing commercial potential, Kellogg sold grinders to health-food stores. Within a decade, producers began selling jarred peanut butter.

For 20 years, peanut butter remained an expensive niche food. Teahouses sold peanut butter sandwiches as a trendy accompaniment to their beverages. When commercial production of peanut butter took off in the 1920s, the price dropped. Its popularity increased when manufacturers learned to add hydrogenated fat to prevent the oil from separating (a process developed in 1922 by the founder of Skippy), but sales really went through the roof as manufacturers added increasingly stiff doses of sugar. World War II cemented the importance of peanut butter in America, as the scarcity of meat required citizens and soldiers to seek protein alternatives.

Legendary agriculturalist George Washington Carver's role in peanut history, although significant, is sometimes overstated. During a boll weevil infestation of the deep South in the 1910s and 1920s, Carver urged cotton farmers to switch to peanuts, and he recommended many uses for peanuts that he adapted from other sources. But peanut butter was not among them. Carver's promotional activities resulted in substantial Southern cultivation of and increased demand for the crop, but Virginia and the Carolinas were already prodigious peanut producers, and few of Carver's peanut concoctions remain popular.

Were Carver alive today, he would have much work to do: Demand could really use a boost. The USDA projects an annual peanut surplus of 850,000 tons, and the salmonella outbreak could push the surplus over 1 million tons. Many farmers may have to accept government-backed loans of $355 per ton (less than the cost of production) and hope that prices rise while they store their unsold legumes in warehouses.

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Explainer thanks Andrew F. Smith, author of Peanuts: The Illustrious History of the Goober Pea, and Nathan B. Smith of the University of Georgia.

Correction, Feb. 13, 2009: This article originally identified John Harvey Kellogg as a "breakfast-cereal titan." It was Will Keith Kellogg who founded the Kellogg Company. (Return to the corrected sentence.)

Brian Palmer is Slate's chief explainer. He also writes How and Why and Ecologic for the Washington Post. Email him at explainerbrian@gmail.com. Follow him on Twitter.