Candy bars may seem quintessentially American, but they have origins in the World War I chocolate rations given to European soldiers. The American military followed suit, helping its doughboys develop a sweet tooth they would bring home after the war. Throughout the 1920s, thousands of small, regional confectioners emerged to meet the demand, creating a candy boom brimming with catchily named bars based on popular expressions, pop culture icons and even dance crazes. (Hello, Charleston Chew.) The goal of the most ambitious new sweets makers? To take a bite out of a candy business dominated by Hershey’s, the planet’s biggest chocolate maker.

While the history of chocolate consumption stretches back 4,000 years to ancient cultures in what is today Mexico and Central America, the U.S. story of chocolate has strong military associations.

In the earliest decades of the United States, candy was quickly recognized not just as a sweet treat, but as a valuable way to fuel troops. During the Revolutionary War, chocolate, a favorite treat of George Washington, became part of his soldier’s rations. It was prized for its combined kick of caffeine and sugar; it even served as occasional payment to American troops in lieu of money. Candy also played a role in the Civil War, used as “a provision with quick energy and lots of sugar,” says Steve Almond, author of Candyfreak: A Journey through the Chocolate Underbelly of America.

While the first chocolate bar was created by Joseph Fry in Great Britain in 1847, and Cadbury began selling individual boxes of chocolate candies there as early as 1868, it would take the outbreak of war on a global scale for the chocolate candy bar to really take off.

In World War I, the British military gave soldiers chocolate to boost morale and energy. The Mayor of York sent a tin of hometown confectioner Rowntree’s chocolates to residents in uniform, and in 1915, every U.K., soldier abroad received a “King George Chocolate Tin.”

Not to be outdone, the American Army Quartermaster Corps solicited donations of 20-pound blocks of chocolate from confectioners back home, which they then cut down and wrapped by hand. When U.S. GIs returned from the war with an insatiable appetite for chocolate, they arrived back just before the onset of Prohibition—when Americans actively sought alternatives to alcohol to boost their energy and mood, from soda to ice cream to candy. By the end of the 1920s, more than 40,000 different candy bars were being made in the U.S., says Susan Benjamin, candy historian and author of Sweet as Sin: The Unwrapped Story of How Candy Became America’s Favorite Pleasure.

During the candy bar boom, nearly every major city had a set of confectioners cranking out as many types of candy bars as they could, filling them with everything from nougat, marshmallow and nuts to fruits and dehydrated vegetables. (Yes, really.) Because a lack of widespread refrigeration and transportation issues remained a barrier to national distribution, regional brands dominated each market, creating bars with names that appealed to local pride. The Charleston Chew took its name from a local dance craze. The 18th Amendment Bar was born in Chicago during Prohibition. “It was the birth of modern marketing. Since most bars used the same six or seven ingredients, people were furiously trying to figure out how to differentiate their brand,” says Almond.

Candy companies often named their popular bars after pop culture icons: “Charles Lindbergh begat both The Lindy and Winning Lindy. Clara Bow begat the It bar. Dick Tracy had his own bar. So did Amos ’N’ Andy and Little Orphan Annie and Betsy Ross,” Almond says.

One chocolate baron recognized for his marketing genius was Otto Schnering of the Curtiss Candy Company. He had the audacity to fudge the name of the Baby Ruth bar—claiming he named it for President Grover Cleveland’s daughter, while conveniently cashing in on the popularity of baseball legend Babe Ruth. (The slugger later tried to get in on the candy business himself with something called “Ruth’s Home Run Candy,” but Schnering boldly sued him for copyright infringement—and won.) A master of the marketing stunt, Schnering chartered a barnstorming biplane in 1923 to do aerial tricks over U.S. cities like Chicago and Pittsburgh while dropping payloads of Baby Ruth bars, complete with tiny parachutes. Later, Schnering arranged to have his Butterfinger candy bar featured in the 1934 Shirley Temple movie Baby Takes a Bow, pioneering the art of product placement with one of the biggest stars of the era.

Later, during the Great Depression, as Americans had less disposable income for treats, some makers shifted their marketing campaigns to position candy bars as a cheap meal replacement option. “Candy bars became essentially fast food, especially [later] in the Depression era, when people needed quick energy and cheap calories,” says Almond. “Candy bars like ‘Chicken Dinner’ or ‘Club Sandwich’ sent the message that if you don’t have time or money for a full meal, candy bars were a quick and affordable way to eat.”

The Depression slowed the chocolate gold rush considerably, as scarcity and high prices for raw candy ingredients like sugar helped drive many independent, regional confectioners out of business—or into buyouts with larger manufacturers. Hershey's, for example, cut a deal to help support the popular, but financially foundering, Reese’s Cups. With the outbreak of World War II, shortages became even more pronounced. And the military commissioned chocolate rations from America’s biggest producers, spelling an end to the regional candy bar boom.

In 1937, the U.S. Army asked Hershey Company to create the “D-Ration bar.” It had to weigh just four ounces, provide a burst of energy, not melt in high temperatures and “taste a little better than a boiled potato” to prevent soldiers from eating it too quickly. The resulting product was not known for its taste. Hershey’s launched a more palatable product for the Pacific Theater, the “Tropical Bar,” in 1943. By the close of World War II, Hershey’s had manufactured more than 3 billion ration bars.

After World War II, improvements in manufacturing, transportation and refrigeration further challenged hyper-regional confectioners. Large companies bought out smaller ones and provided national distribution. Today, most American chocolate bars are manufactured by the “big three”: Hershey’s, Mars and Nestle, though individual bars like Baby Ruth, Butterfinger and PayDay harken back to the heyday of the American candy bar.