Via Wikipedia:
A traditional style muffuletta sandwich consists of a muffuletta loaf split horizontally and covered with layers of marinated olive salad, mortadella, salami, mozzarella, ham, and provolone. The sandwich is sometimes heated to soften the provolone."
After doing extensive research, I discovered that this incredible sandwich made its debut at Central Grocery, a New Orleans speciality market which opened in 1906. As is the case with most larger-than-life sandwiches which have become mainstays amongst their fans for generations, the Muffuletta was conceived to feed very hungry individuals from a wide selection of ingredients. Central Grocery's owner at the time, Salvatore Lupo, noticed that some of his regulars struggled with deciding on their usual lunch of bread, salamis, cheese and olives. To avoid this conundrum during busy hours, he devised the idea to combine them all into one sandwich. Because such engineering would require immense structural integrity, Salvatore Lupo realized that simply choosing wheat bread would be a complete disaster, but also understood that using toasted Italian bread would be too difficult to bite into. As a remedy, Mr. Lupo looked elsewhere...to muffeletta bread.
A muffeletta is a round Sicilian sesame bread, typically 10 inches in diameter, and sometimes flattened to make handling easier.
Until the 1960's, The Muffeletta Sandwich (as it became to be known), mostly remained popular only to residents of New Orleans. However, around the same time that Neil Armstrong made his first "small steps," these sandwiches became quite popular in various Italian communities across the country, most specifically the Chicago and New York markets.
On a personal note, my first taste of a muffeletta sandwich (albeit a variety that isn't completely accurate with Salvatore Lupo's creation) took place at Schlotzsky's Deli. First founded in 1971, Schlotzsky's has been offering their take of the sandwich -- known as The Original -- for over 40 years. My dad first took me to a Schlotzsky's Deli in 1998, and I have been a fan of The Original ever since.
However, if you ever find your self in N'awlins, I strongly urge you to make your way to Central Grocery to taste a sandwich that has been delighting customers for the past century. I did so myself back in February of this year, and it was a true honor and privilege.
DISCLAIMER: While I'm not being paid to write this article, I would endorse some sort of reward for doing so. Perhaps a free sandwich?
Obligatory food porn.