The origins of the brownie are somewhat mysterious and controversial. Chicago’s Palmer House Hotel, cookbook author Fannie Farmer, and an unknown housewife in Bangor, Maine, all have some claim on its creation.
I’ll start with the Palmer House story, which is that its kitchen invented little chocolate cake bars glazed with apricot preserves and decorated with nuts for the 1893 Columbian exposition, and named these treats brownies. They were made to put in boxed lunches for ladies attending the exposition. According to The Oxford Encyclopedia of Food and Drink in America, this legend may be true, and the hotel served brownies like these later on — and still does — but there is unfortunately no documentation for the 1893 date.
Fannie Farmer was the first to actually publish a recipe for brownies, in 1896. Her creation was different from the modern brownie (and Palmer House’s), as it had no chocolate and wasn’t cut into bars. But the texture was brownie-like, and she followed it up a decade later with a recipe more like the brownie as we know it today.