Humans have been combining bread and cheese together for centuries. Even the Ancient Romans put together recipes for cheese melted on top of bread.
The modern American grilled cheese is a more recent invention. In the early 1900s, a young man named James L. Kraft was pushed out of his partner's business and stranded in Chicago with only $65. Kraft bought a mule and purchased cheese wholesale and sold it to local grocers. Kraft soon realized that the major problem with cheese was spoilage; most restaurants and store owners did not have refrigerators so cheese wheels had to be used within a day of cutting.
In 1915, James L. Kraft invented a way to manufacture a blended, pasteurized cheese that he called "processed cheese." This pasteurized cheese could be transported across the country without spoiling. He patented his invention in 1916 and soon began selling Kraft cheese across the country.
Early grilled cheese sandwich recipes were made by mixing the grated cheese with a binder, such as salad dressing or white sauce or mustard, and toasting the sandwich between two slices of buttered bread. These were called "Toasted Cheese Sandwiches."
During World War I, the United States Army purchased 6 million pounds of Kraft's cheese. In World War II, Navy cooks prepared countless "American cheese filling sandwiches" for hungry Naval seamen.
Depression-hit families also found processed cheese to be a cheap and filling meal. (Kraft sold nearly 8 million boxes of its macaroni and cheese during the Depression, under the marketing campaign that you could feed a family of four for 19 cents.) School cafeterias purchased cans of tomato soup to go with toasted cheese sandwiches to satisfy the Vitamin C and protein requirements for school lunches, leading to the classic childhood combination.
Soon, grilled cheese sandwiches were everywhere. A 1934 Washington Post article explained, "Sunday night is a grilling time. Avoiding a pun is difficult, but modern cooking being what it is and modern tastes being what they are, the statement stands and may be accepted quite literally. Grilled cheese sandwiches are no new thing. We get them in drug stores for lunch and at tea rooms for supper. But when the housewife begins to grill there is no limit to the combinations she may use and the delicious Sunday night suppers she may serve.
Open-face sandwiches of cheese and tomato grilled, offer a combination of flavors sure to please the palate."
In 1949, Kraft Foods introduced Kraft Singles—individually wrapped slices of processed cheese—and it became even easier for home cooks to make grilled cheese sandwiches.
Today, grilled cheese is making a resurgence with gourmet versions popping up in restaurants across the country and people exploring international varieties of grilled cheese sandwiches.