Holiday tables are often divided over these three little words–green bean casserole. This mixture of canned soup, frozen green beans and fried onions has graced holiday buffets since the 1950s. But who came up with this trinity, and why has it become so famous? This week we’ll take a look at green bean casserole, from its humble origins in a test kitchen to the love-to-hate-it dish we know today.

As anyone who’s checked out the kitchen section of an antique store can attest, recipe pamphlets were once a big business. Long before the Internet, home brands like General Mills, Cuisinart and Ball Jars regularly released these pocket-sized magazines full of tips, recipes, and instructions for their products. Glossy covers depicted the cakes or pot roasts detailed inside, and housewives loved them for their price and ease of use: why pay for a heavy cookbook when a recipe pamphlet could provide the same information for less money?

The Campbell’s Soup Company had its own kitchen, in Camden, New Jersey, dedicated to pumping out recipe pamphlets. A home economist named Dorcas Reilly worked at the Campbell’s kitchen, and in 1955 she successfully devised and tested the infamous green bean casserole recipe. In numerous interviews Reilly gave years later about the invention of the casserole, she professed to not remember exactly how she came up with that specific dish. Campbell’s Cream of Mushroom variety had been around since 1934. It was widely used as casserole filler in the Midwest, popping up in enough Minnesotan hotdish recipes that it was sometimes referred to as “Lutheran binder.” But no one thought to add frozen green beans to the mix until Reilly came along. The fried onions on top were an easy way to add texture and brighten the color of a grey-green dish, and to add a certain festive touch to the proceedings.

Reilly’s recipe was immediately popular. It was the perfect recipe for the holidays, as it was made with minimal ingredients that were almost always on hand, and it could easily be made the day ahead and reheated when guests arrived. And its popularity continues today, even in the face of America’s recent obsession with fresh, locally grown, artisanal foods. Campbell’s now estimates 40% of the Cream of Mushroom soup sold in the US goes into making green bean casserole.