In the 1900's, the sandwich became popular in the USA when American bakeries started selling sliced bread. Sandwiches were an easy, portable meal for skilled and non-skilled trades such as railway workers, carpenters and miners, as well as, school children.
Cream cheese had been invented in New York (1872) but became mass marketed by the American, Philadelphia Brand in 1928. That brought on the American Cheesesteak, hamburger, hot dog, peanut butter sandwich and the incredible Sloppy Joe -- ALL created or invented by Americans.
In the 20s, the luncheonette brought fame to hot sandwiches. Warm meat could be carved and placed on bread topped with hot gravy.
World War II years created popular sandwiches, such as the hero, hoagie, grinder, submarine, Po' Boy and torpedo.
Americans from various parts of the country began their own version of the sandwich. There's the Denver Omelet (eggs on toast), Fluffernutter (peanut butter and Fluff marshmallow creme, a New England invention), French Dip created in Los Angeles (sliced roast beef on French roll or baguette au jus).
There's the Muffaletta from New Orleans, with ingredients similar to a hero or sub, but served on a slice cut from a loaf of round Sicilian muffaletta bread, instead of a long roll; Philadelphia Cheesesteak (thin slices of grilled steak with melted cheese on a roll; the ever popular Reuben Sandwich from New York City—pastrami, sauerkraut and melted cheese on pumpernickel or rye bread.
World War II soldiers combined mess kit C-Ration crackers with peanut butter and jelly, and Elvis Presley made the fried peanut butter and banana sandwich his foodie fare.
The next gen began putting "extras" on sandwiches, such as crunchy potato chips and french fries. Salt and Vinegar "Chips" complimented fried fish sandwiches. BBQ "Chips" went well with the turkey sandwich.
The Reuben married the dill pickle; and the Torta got engaged to sour cream and onion "chips."
According to Blondie scripter Dean Young, his father, Chic Young, began drawing the huge Dagwood sandwich in the "Blondie" comic strip in 1936.
Named for the comic strip character, Dagwood Bumstead, the sandwich contains healthy amounts of cold cuts, sliced cheese and vegetables separated by more than one slice of bread. An olive skewered by a toothpick crowns the edible tower of goodness.
If you watch Guy Fieri on Food Network's Diners, Drive-Ins and Dives, you see many different mouth-munching smiley faces enjoying all sorts of hot and cold sandwiches.
Esquire has a list of the best sandwiches in America,