The concept of the “free lunch” began in America in the 1840s, probably in New York City. The idea is that people would pay for their drinks. Free lunches were popular in many other cities, such as Baltimore, New Orleans, and San Francisco. Free lunches are not offered today, and the term is largely a 19th century one.
 
There are also the phrases “There Ain’t No Such Thing As A Free Lunch” (TANSTAAFL) and Fiorello La Guardia’s “No more free lunch!”
 
   
Wikipedia: Free Lunch
The phrase free lunch, in U. S. literature from about 1870 to 1920, and in the currently popular proverb “there ain’t no such thing as a free lunch,” refers to a tradition once common in saloons in many places in the United States. These establishments offered “free” lunches, varying from rudimentary to quite elaborate, with the requirement that the partaker purchase at least one drink.
 
Many writers agree that these free lunches were typically worth far more than the price of a single drink. The saloon-keeper relied on the expectation that most customers would buy more than one drink, and that the practice would build patronage for other times of day. The nearly-indigent “free-lunch fiend” who came for the food and bought only one drink—or bummed one from strangers—or attempted to leave without buying one—was a recognized social type: a character in a 1919 novel describes a battle by saying “the shells and shrapnels was flyin round and over our heads thicker than hungry bums around a free lunch counter.”
 
The saying “there ain’t no such thing as a free lunch” refers to this custom in a back-handed way, meaning that free things often have hidden costs.
 
In 1872 The New York Times wrote of elaborate free lunches as a “custom peculiar to the Crescent City” (New Orleans), saying that “in every one of the drinking saloons which fill the city a meal of some sort is served free every day. The custom appears to have prevailed long before the [American Civil] war…. I am informed that there are thousands of men in this city who live entirely on meals obtained in this way.” As described by this reporter,

“A free-lunch counter is a great leveler of classes, and when a man takes a position before one of them he must give up all hope of appearing dignified…. all classes of the people can be seen partaking of these free meals and pushing and scrambling to be helped a second time. [At one saloon] six men were engaged in preparing drinks for the crowd that stood in front of the counter. I noticed that the price charged for every form of liquor was fifteen cents, punches and cobblers costing no more than a glass of ale.”   
 
(Oxford English Dictionary)
free lunch, a lunch given gratis, esp. by bar-keepers to attract customers
1854 Wide West (San Francisco) 26 Nov. 2/3 The excitement during the week on the subject of the ‘*free lunches’ has been of the most intense character. 
 
29 July 1847, Louisville (KY) Morning Courier, pg. 3:
Messrs. O’MARA & GORDON open their “Washington Exchange,” formerly the Washington Hall, to-day, with a free lunch.
 
4 July 1848,  New York Herald, advertisement:
EADIE’S COFFEE HOUSE, 196 FULTON STREET,—GEORGE EADIE respectfully intimates that having fitted up the above establishment, he will be happy to see his friends on the 4th of July.  Steaks, Chops, and Scotch Mutton and Veal Pies, always on hand.  Brandies, Wines, and Liquors, of the first quality. Free Lunch at 11, A.M.
 
13 February 1849, Bangor (ME) Daily Whig & Courier:
We yesterday received a copy of the Corpus Christi Star, from Capt. Charles G. Bryant.  He now advertises as the proprietor of the Union House, where “a free lunch is set every day at the Bar, at 11 o’clock.”
 
28 October 1951, Brooklyn Daily Eagle, pg. 2 ad:
...CHARLEY FISDECK, corner of Myrtyle avenue and Duffie’d street. He has all the newspapers, serves up a FREE LUNCH every day, keeps good oysters and the most superior drinkables in the State of Long Island.
 
20 July 1889, Brooklyn Daily Eagle, pg. 3:
FREE LUNCH.
The Evolution of a Popular Repast.
(...)
When the custom of serving free lunches in barrooms was first instituted is not definitely known, as the entire library is silent on this point. The best information that can be obtained, however, on its introduction in Boston, was pumped out of a gray haired bartender, who is widely known throughout the trade in this city. Said he: “The first thing of the kind that I remember, and my memory runs back nearly forty years, was started by a man named Stinson, who kept a place on Congress Street, near State. His bill of fare consisted of hashed fish, and, by the way, it was the finest hash I
ever ate, pork scraps, beans and soup.  He did an immense business when he first put the sceme into operation. He had many imitators later on, and finally all the barrooms in the city vied with each other in the excellence of their gratuitous lunches.”