Well...you might start from the very top: what is "popular culture?" The thing about history is that most of the stuff that comes down to us is what is preserved - usually (but not necessarily) the important bits like the Bible and major chronicles and papal bulls and that kind of documentation, but what we often miss out on is the everyday stuff which although critical to contemporary attitudes and life may never have been recorded, or if recorded not saved or archived because it wasn't perceived as important - if there was a sudden fad for alcoholic chocolate drinks in Central America 600 years ago, for example, or wearing a red stripe on your dress was the symbol of a prostitute in France in 1500, we might not know; or maybe no one wrote down what the favorite songs were in England in 1333, or the favorite ghost story to tell around the hearth in 666. None of that is necessarily high art, or important to the ruling castes, but it is nevertheless an important part of everyday life in those times, which helped influence thought in many communities.

The burgeoning of what we call "popular culture" of the 20th century is fueled in part by a recognition that this is culture - and by the increasing connections between communities, the heightened degree of literacy, and the improved recording and distributing technologies and media that allowed that culture to be spread and made widely available.

Put this another way: in the Renaissance, culture spread at the speed of a horse (or a sailing ship). For a highly illiterate population, what they knew was largely relegated to what they could see with their own eyes and hear with their own ears. But as we inch closer to the contemporary period, trade networks get more robust, musical notation becomes formalized and exchanged, iconography and even languages become standardized, literacy rates start to rise, books become mass produced (followed by newspapers and other periodicals), and then in the 19th century...you get the invention of the telegraph, telephone, and finally the radio. Photography, musical recording, and then video recording enable us, more easily and effectively than ever before, to capture and share the same experiences.

It gets to the point in the 20th century that we can effectively realize - and talk about - a shared culture on a scale never seen before. People on every continent know what McDonald's is, and can recognize Ronald McDonald; people that can't read English can still recognize the shape of a Coca-Cola bottle. That's a huge change from a century ago! Two centuries ago, it would have been almost inconceivable.

For a solid introductory text into some of the ideas behind this, you might want to look at Marshal McLuhan, especially Understanding Media (1964) and The Global Village: Transformations in World Life and Media in the 21st Century (1989).

For some specific examples you might look at Scott McCloud's Understanding Comics: the invisible art - the first couple of chapters especially trace how comics evolved as the media did - and The Rise and Fall of Popular Music: A Narrative History from the Renaissance to Rock'n'Roll by Donald Clarke.

I am planning some projects like "If Jean-Michele Basquiat had Twitter, what would his Tweets look like" or "What would Warhol's Snapchat consist of?" filling a contemporary pop tech culture and pop art niche but aside from a few points here and there, I could really use some of the decades between 1900-1999 fleshed out.

While it might be engaging to have the students approach it from today's trendy ubiquitous media perspective, most pop culture is very much about the context of the era. In the United States that would involve things like World War I (1914-1918), Prohibition (1920-1933), the Great Depression (1929-1939), World War II (1939-1945), etc. - but concurrent with that, driven by and driving events, is the popular culture. Prohibition coincided with the Jazz Age; during the Great Depression millions of Americans tuned in to presidential fireside chats; wartime propaganda invaded every medium, from radio serials to comic books to the burgeoning motion picture and television industries... It's not about pulp magazines and singing telegrams versus tweets and YouTube accounts; it's understanding what the difference was between popularity then as opposed to popularity now, and yet how even though technology has changed, the basic approaches to storytelling largely haven't. You might for example draw a parallel between Hollywood remaking films in the 2010s versus Hollywood remaking films in the 1920/30s (as silent films gave way to talkies) - we think of remakes as a groan-worthy example of Hollywood's creative breakdown today, but ask your students: What did they say about them back then? How was it different? (Hint: If you missed seeing a film in the theater in 1925 - or a play on Broadway - when would you get to see it again? If you missed seeing a television show in 1955, when would you be able to catch a rerun of it?)

That's sort of what I mean about pop culture being ephemeral - for the most part, prior to the 1950s if you missed it you missed it (it being anything: a song, a story, a radio programme, a movie, etc. - even most books, once they went out of print, could be difficult to find.) The ability to have access to media "on demand" is a huge change that has massively effected popular culture, because it gives us access to a huge depth of culture that was, frankly, lacking in earlier times - and that in turn has generated a lot of perspective, remixing, updating, and analysis that just wasn't possible beforehand.

I think I've probably gotten off track a bit here as I bled into history of technology stuff, so I'm going to stop, but I hope some of that is helpful.

You've got to talk about advertising, video games, MTV!

You could do a unit on the influence of African American blues on the invention of rock music. That's a huge topic in itself with influences that are still felt today.