The invention of the cheeseburger is generally credited to Lionel Sternberger, a 16-year-old who worked at his father's sandwich shop called The Rite Spot in Pasadena, California. Around 1924, he is said to have added a slice of American cheese to a sizzling hamburger patty, either as an accidental "cheesy cover-up" for a burnt patty or at the request of a customer. This creation was initially called the "Aristocratic Burger" and is recognized as the first known cheeseburger served on a menu.

There are competing claims, such as Kaelin's Restaurant in Louisville, Kentucky, which claims to have invented the cheeseburger in 1934, and Louis Ballast in Denver who trademarked the name "cheeseburger" in 1935. However, Lionel Sternberger's 1924 contribution is the earliest documented origin.

In summary, Lionel Sternberger is most widely acknowledged as the inventor of the cheeseburger, making the first known cheese-topped hamburger in Pasadena, California in the early 1920s.