While we can thank Germany for the Frankfurter (via How Stuff Works), can the hamburger really trace its origins to the German port city of Hamburg, or is this just a myth? According to the Online Etymology Dictionary, the hamburger is "the meat product so called from 1880 (as hamburg steak), named for the German city, though no certain connection has ever been put forth." The idea of the hamburger, however, might have appeared in first-century Rome, where there is a record of ground or minced meat that was flavored with pepper, wine, and pine nuts (via Taste of Home).
In the Middle Ages, Central Asia and Eastern Europe were invaded by Mongolian nomads that the Russians called Tartars, according to What's Cooking America. When this group invaded Moscow in the 13th century, they introduced the Russians to the practice of eating raw, shredded beef. The Russians added raw egg and onions and called their version "Steak Tartare."
Sometime in the 1600s, Russian ships brought their delicacy of raw, minced beef to the German port city of Hamburg. In Germany, "Hamburg sausage" was created when the raw minced meat was broiled or fried (via Culture Trip). In the 1800s, minced beef from German Hamburg cows was combined with garlic, onions, salt, and pepper and formed into patties, giving birth to "Hamburg steaks" (via Parade). As Germans emigrated to the United States, they brought with them the recipe for Hamburg steak. Some of these immigrants opened restaurants and food carts in New York, where they featured the item. Most notably, in 1873, New York City's famed Delmonico's menued Hamburg steak for the then-steep price of 10 cents.
But how did this minced beef patty become the sandwich we know as the hamburger? The history isn't completely clear. Some credit brothers Frank and Charles Menches with putting a patty between two slices of bread in the aptly named town of Hamburg, New York, in 1885. Others believe it was introduced by teenager Charlie Nagreen in Seymour, Wisconsin that same year. Relatives of Oscar Weber Bilby claimed he was the true inventor of the hamburger, noting that he put the patty in an actual bun in 1891 in Tulsa, Oklahoma (via What's Cooking America). Finally, the Library of Congress posits the first hamburgers were served at Louis' Lunch sandwich shop in New Haven, Connecticut in 1895.