The long national nightmare is over: KFC is bringing back the Double Down. The no-bun, double-breasted chicken concoction was a legendary milestone in fast food engineering, changing the very way people thought a sandwich could be made. ("Hey! What if the meat was actually the bread?")

The Double Down (which returns on April 21) might be the apex of fast food innovation, but the road to this point is a spacious four-lane drive-thru of gastronomical disruption. No one thinks outside the Styrofoam box quite like the giants of the fast food industry, and in honor of their achievement we decided to take a look back at some of the seminal moments in food science.

The beginning of fast food history, as you might expect, is dominated by McDonald's, the grandaddy of them all. But the chain has gotten lax in the past decade or so, leaving upstarts like Taco Bell and KFC to surge ahead, and in the process creating new wonders of the fast food world. These are the moments that changed fast food history — and our world — forever

 

Correction: The timeline states the Fried Chicken Crust Pizza is from Pizza Hut. It's actually from Domino's. 

Big Mac – 1968

The one that started it all: Two all beef patties, special sauce, lettuce, cheese, pickles, onions, on a sesame seed bun. There have been many imitators, but there has only been one Big Mac.

Subway – 1968

No specific menu item is that unique, but the whole concept behind the Subway franchise was a game changer. Fresh, made-to-order sandwiches, with real vegetables, in the blink of an eye? Subway let us sort of feel good about eating fast food. And then that whole $5 foot-long deal, damn.

Frosty – 1969

Not quite ice cream, not quite a milkshake, the Frosty is a work of art. It’s nearly possible to go Wendy’s and not buy one, and it proved that fast food can do dessert too. For a while, chocolate was the only option, but that’s fine. Because if you get vanilla, you’re probably a monster.

McMuffin – 1972

Fast food for breakfast: so simple, so beautiful. The Egg McMuffin got us out of bed early for some let’s-pretend-it’s-really-egg, (Canadian) bacon, and cheese, all on an English muffin. The perfect one-handed, on-the-go start to your day. It's such a big deal, in fact, that the inventor got an official obituary by the Associated Press. Next step: serving it all day.

McRib – 1981

The cult favorite. The McRib inspires intense passion in a select few of us — in part because its limited availability makes it a rare and momentous treat — and it is the poster child for specialty fast food items. There was even a Simpsons episode about it, so come on.

McNuggets – 1983

Can you believe McNuggets weren't a (nationwide) thing until the 1980s? Now you can't imagine any fast food restaurant (and a lot of not-so-fast food places) not having bite-size chicken pieces somewhere on their menu, dipping sauces and all.

McDLT – 1984

A noble pursuit. In 1984, McDonald’s attempted to solve one of fast food’s toughest predicaments: how do you keep the cold stuff (lettuce, tomato, etc) cold and the hot stuff (burger, cheese) hot? The answer was two Styrofoam chambers linked into the service of one sandwich. And it worked for a few years before environmentalists got all fussy and McDonald’s pulled the plug. 

Chipotle – 1993

Like Subway, but for burritos. Also that whole organic thing, I guess.

Double Decker Taco - 1995

Everyone loves a crunchy taco, but they don't like when they fall apart in your hand when the shell inevitably shatters. So what about a protective layer of soft tortilla, cemented to the foundation with refried bean glue? The day is saved.

Pizza Hut Stuffed Crust – 1995

Is pizza fast food? If it’s Pizza Hut, it is, as few restaurant chains anywhere have done more to revolutionize the way their signature foodstuffs are made. The introduction of stuffed crust was a seminal moment in chain pizza history. Cheese, inside the crust. Pizza, you eat back-to-front. Madness.

BK Chicken Fries – 2005

The best thing to happen to chicken since the McNugget. Burger King’s “fit in your cup holder” chicken fries combine two favorites – chicken nuggets and French fries – into one beautiful, portable menu item.

KFC Double Down – 2010; 2014

A gluttonous testament to American ingenuity. Forget bread: let’s stuff melted cheese and bacon in between two pieces of fried chicken instead. Can’t wait until all fast food items are bun-less and the meat is doubled.

Doritos Locos Taco – 2012

So simple and elegant, you wonder how humanity ever lived without it. A taco with the shell of a giant Dorito. It’s sort of unbelievable this hasn’t put all other fast food chains out of business yet.  

Taco Bell Waffle Taco – 2014

Taco Bell is definitely winning the fast food innovation war lately. Instead of making the taco shell a giant chip, this time they made it a waffle, and loaded it up with sausage, egg, and syrup. You could eat this for more than just breakfast, honestly. 

Domino’s Fried Chicken Crust Pizza – 2014

Not really pizza and not really fried chicken, Domino’s newest concoction is some Frankenstein-esque jumble of fried chicken, cheese, and various toppings. What we’re thinking now: What if we sandwiched this in between two giant Doritos? Now, that's what I call a taco!