The hamburger’s origin story - The Washington Post
"Who invented the hamburger? Biting into the messy history of America’s iconic sandwich."
One popular story goes that in 1900 a customer walked into Louis’ Lunch in New Haven, Conn., and asked for something he could eat on the go. Owner Louis Lassen improvised by giving him a patty of the restaurant’s steak trimmings between two pieces of toast. The customer got his carryout lunch, and the world got the hamburger sandwich.
Except that that was far from the first.
In January I wrote a story that raised questions about Louis’ Lunch’s standing as the birthplace of the hamburger. However, I was not able to definitively disprove the claim. After the story ran, a reader named Thomas Pieragostini emailed me a link to a series of ads that appeared in the Shiner Gazette in Texas in the spring of 1894 that advertised “hamburger steak sandwiches” being served at a local saloon.
noting
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This early burger reference inspired me to dig deeper, and I have since found more than a dozen newspaper references to hamburgers in the 1890s, including in Virginia, Illinois, Iowa, Nebraska, Nevada, New York, California and Hawaii. These findings debunk the Louis’ Lunch claim and suggest other burger origin stories are not true, either. ...
Going back further,
But the true precursor to the burger we know today seems to be an inexpensive dish called hamburger steak, which began appearing on American menus in the early 1870s. (A menu, allegedly from Delmonico’s in New York City in 1834, listed the dish. It was eventually exposed as a fake.)

These minced beef and onion patties were served on a plate, not bread ...
and
In the mid-1700s, “The Art of Cookery Made Plain and Easy” by Hannah Glasse carried a “Hamburgh sausages” recipe, which was served on toasted bread. In Germany, a meat patty on bread called Rundstück Warm was popular by at least 1869.
and
“A first-century A.D. Roman cookbook by Apicius has a recipe in it that is suspiciously close to the modern burger, a minced meat patty blended with crushed nuts and heavily spiced and cooked,” says George Motz, a filmmaker and author who has researched burger history extensively.
This is a kind of Sandwich That name comes from John Montagu, 4th Earl of Sandwich someone who was known for liking to eat that combination food. But sandwiches are older than him.