The oldest dishes at the feast are actually some of the newest

Somebody's grandmother set the first green bean casserole on her Thanksgiving table in the 1950s, and the recipe came from a soup company.

Most families have one Thanksgiving dish nobody is allowed to touch. Surprisingly often, a food company put it there.

The green bean casserole dates to 1955, when Dorcas Reilly, a supervisor in Campbell's test kitchen in Camden, New Jersey, was asked to build a recipe around two things most households kept on hand: green beans and cream of mushroom soup. She called it Green Bean Bake. In 2002, Campbell's donated her original recipe card to the National Inventors Hall of Fame. Reilly later said in interviews that she did not remember creating it. Her department turned out recipes by the hundreds, and that one did not stand out at the time. She insisted it was a team effort.

Marshmallows on sweet potatoes arrived much the same way. Candied sweet potatoes are far older, but the topping was a sales idea. In 1917, the makers of Angelus Marshmallows hired Janet McKenzie Hill of the Boston Cooking School Magazine to write a booklet coaxing cooks to use marshmallows as an everyday ingredient. According to the Library of Congress, that booklet holds the first documented recipe for mashed sweet potatoes baked under a marshmallow topping.