As the 19th century gave way to the 20th, Americans woke up to a new kind of breakfast: cold cereal. Poured from a box into a bowl and doused with milk, early cereals like Toasted Corn Flakes, Grape-Nuts and Shredded Wheat were not only lighter and easier to digest than more traditional breakfast staples like steak and eggs, hash, sausage, bacon and flapjacks. They also offered a previously unimaginable level of convenience to men, women and children whose schedules were adjusting to the quicker pace of an industrialized, rapidly urbanizing nation.

Cereal's origin story has a few competing versions. What's not in dispute is that it likely first emerged in the late 1890s from the kitchen of the Michigan-based Battle Creek Sanitarium, an early health spa started by Dr. John Harvey Kellogg, one of America's first wellness gurus. The cereal story involves fraternal strife and even features an appearance by future Kellogg competitor C.W. Post, an early patient at the spa who paid his way, in part, by working in the kitchen. Post saw the cereal evolution happening firsthand—and moved to profit from it himself.

“In the colonial period, people—especially ordinary working-class people—had a tendency to eat either porridge or leftovers from the night before,” says culinary historian Sarah Wassberg Johnson. But as the new nation grew wealthier, she explains, breakfasts got bigger. “There's a trend that started with the European aristocracy, to have this giant breakfast buffet with cold-smoked tongue, ham, sausage and egg dishes and things like that.”

In the 19th century, however, large breakfast spreads became commonplace, especially after the industrialization of beef and pork production in Midwestern cities like Chicago and Cincinnati. This was particularly true in rural areas, where large, meat-heavy morning meals fueled farmers and laborers for their days of work.

Then came the Industrial Revolution, which revolutionized the nature of work. More people were laboring in factories, shops or offices, which ran on standardized schedules, leaving less time for food preparation and consumption during the workweek.

Increasingly, a heavy morning meal also wasn’t considered ideal for health reasons. Diseases such as tuberculosis (then called consumption) plagued many Americans at the time. So did digestive ailments, likely linked to a typical diet high in refined carbohydrates, sugar and meat.

“At the turn of the century...especially with the influence of Teddy Roosevelt and his endorsement of what he called the "strenuous life," there's a resurgence of interest in health and athleticism,” Wassberg Johnson says. “We're recovering from the excesses of the Gilded Age, both economically and morally, and in terms of what we eat.”

Dr. John Kellogg helped lead the movement toward cleaner living. Raised in the Seventh-day Adventist Church, which believed in the imminent end of the world and the second coming of Christ, Dr. Kellogg had been groomed by the church’s founders to be a leader in the faith. In 1876, he took over a church-founded health institute in Battle Creek, Michigan, which he built into the world-famous medical spa and resort known as the Battle Creek Sanitarium.

Building on Adventist health principles like eating a vegetarian diet and avoiding alcohol, tobacco and caffeine, Kellogg’s philosophy of “biologic living” emphasized regular exercise, massage therapy and drinking plenty of water. He focused particularly on patients’ digestive health, decrying the evils of fatty, greasy, salty or spicy foods—and endorsing regular powerful enemas to clear out one’s digestive tract. Having studied gorillas in zoos, and seeing that they had four to five bowel movements a day, he prescribed his patients to do the same—and tried to serve foods that would help that process along.

Around 1877, Dr. Kellogg concocted a twice-baked mixture of flour, oats and cornmeal, which he began smashing into small pieces for serving (after a patient broke her tooth on a biscuit version). He believed that by baking the whole grains at high temperatures, a process he called “dextrinization,” they became more easily digestible, and therefore more healthy.

As medical historian Howard Markel writes in his book The Kelloggs: The Battling Brothers of Battle Creek, tracing the exact origins of Kellogg’s Corn Flakes is difficult, due to the many competing versions of the story. Kellogg’s wife, Ella, and his brother, Will, who worked as his assistant (and did much of the administrative work necessary to run the sanitarium), worked alongside him in the kitchen, and both lay claim to playing a role in the flakes’ invention—as do several other family members and Sanitarium employees.

According to company history, it was one night in 1898 when a batch of wheat-based cereal dough was accidentally left out for an extended period of time, causing it to ferment. When rolled out into thin sheets, the slightly moldy dough produced perfect large, thin flakes that became crispy and tasty in the oven. Over the next several years, Will Kellogg kept experimenting with the recipe and figured out that corn, rather than wheat, produced even crunchier, crispier flakes.

Patients at the “San” loved the new cereal flakes, which Dr. Kellogg called Granose (a combination of “grain” and the scientific suffix “ose,”or metabolism). Will Kellogg, meanwhile, saw the opportunity to market the flakes to ordinary people looking for a light, healthy breakfast.

After years of humiliating treatment by his brother—including being forced to take dictation while John was on the toilet—Will bought the rights to the flake cereal recipe and struck out on his own, founding the Battle Creek Toasted Corn Flake Company in 1906. Adding malt, sugar and salt to the dough, he began manufacturing Kellogg’s Corn Flakes in mass quantities and pouring much of the profits into advertising.

By 1909, according to Markel, Will’s company was churning out 120,000 cases of Corn Flakes a day. John Kellogg, who resented his brother’s success, later fought him for the right to use the family name. The resulting legal battle ended in 1920, when the Michigan State Supreme Court ruled in Will’s favor, due to his success at popularizing his now-ubiquitous product.

By the time Will Kellogg entered the market, others had already begun to capitalize on the general public’s appetite for cereal. Among the most successful was C. W. Post, a one-time patient at the Battle Creek Sanitarium who adapted Kellogg’s cereal recipe into his own mass-produced version, Grape-Nuts, to tremendous success. A cut-throat competitor to Kellogg, Post even bought exclusive rights to manufacture the cereal-rolling machine needed in the cereal production process—equipment that Will Kellogg originally helped design.

With the completion of the transcontinental railroad in the late 19th century, the United States was now linked to an unprecedented degree, creating a mass market for Kellogg, Post and other newly recognizable packaged-food brands to ply their wares. Despite the sometimes outrageous claims made in their advertising (Post, for instance, claimed that Grape-Nuts cured everything from rickets to malaria), the growing variety of brand-name companies promised a certain level of quality and uniformity, especially as Americans began to consume processed foods in mass quantities for the first time.

With their irresistible combination of health claims and convenience, combined with the unique circumstances of the historical moment in which they emerged, Kellogg’s Corn Flakes and other cereals would have a revolutionary impact on American breakfast. “It was so easy compared to any other kind of breakfast,” says Wassberg Johnson. “You open a box, dump it in a bowl, pour some milk on it. You really can't get much easier than that in the morning.”