When/Why did American television change from primarily episodic to primarily serialized?

I think it has to do with how technology has changed since then. During that time, we could only 'time-shift' TV shows with:

1. VCRs (notoriously hard to program)
2. Betamax (while it lasted)

Now we have:

1. DVRs (TiVo, from your TV service provider, etc)
2. Internet/Digital video services (Netflix, Hulu, network websites)
3. DVDs and Blu rays.
4. Video On-demand.

So, I would argue the risk of creating a serialized show is greatly reduced because of these factors. The barrier of entry is lower now than at any other point prior to now. Content producers realize that in addition to syndication, they make a tidy bit of revenue on Season TV DVD/BD sales. For example, DVD Sales were cited as one of the reasons Family Guy, while not being a serialized show, was brought back from cancellation.

As far as when this shift happened, I would say it was the success of 24 and Lost that made the serialized drama a possibility on a more broad scale (among network and cable channels). If someone, be it a friend, a co-worker, or a geek off the street, says "Show XYZ" is amazing and you should watch it, then I can just Google it and access it however it's available. 20+ years ago, this was very unlikely to happen due to the availability (lack) and cost of prior TV content (high). Everybody is trying to be the next '24' or 'Lost.' Fox has even brought '24' back for a limited 12 episode mini-series in a slightly different format. I would say that the serialized drama gives viewers a much different relationship to the characters on a TV show.

The difference between the serialized shows of today and the episodic shows of yesterday is that the 'cliffhanger' is weekly versus seasonally and the occasional two-part episode or "mid-season" finale.

I would hazard a guess that, if you were a kid in the 70's/80's that you may just not have watched many of the serialized shows. (of course, I was a kid in the 80's and remember watching all of these...) Off the top of my head, from the 80's, you've got:

• Hill Street Blues
• St. Elsewhere
• Cheers
• M.A.S.H.
• Moonlighting
• Family Ties
• L.A. Law

These were all shows that had long story arcs and episodic consistency...

I think it shifted about the time PrimeTime Soaps began to wane.

I recall several episodic shows when I was young. Virtually all the Adventure and Crime Dramas of the '80s were episodic in nature. From a writer's point of view, it may have been an attempt to keep the shows accessible to a new writer or a fill-in script. Actor contracts, also, went by season. So you knew there would be no cast changes until the season finale or premiere.

The first non-soap shows I recall having a serialized nature were X-Files (1993), Lois & Clark (1993), Millennium (1996) and Buffy (1997).

Note, however, two distinct factors that show up in these-

1. They were all genre-shows, designed for sci-fi fans (known to be comfortable with long stretching plots from reading comics).

2. At this stage the serialization was kept mainly to subplots. It was still years until the serialization would appear in the main stories.

Lost and Alias helped spur that further, as well as other shows such as 24 and La Femme Nikita.

Until we have the present day Walking Dead.

What we remember is clouded by our age. My guess is that you were probably too young to watch it, but, I was able to find an early serialized medical drama called The Nurses for CBS in 1962. It ran for 3 years, was nominated for Emmy awards for Primetime Drama, and was then carried to daytime soap from 1965 to 1967.

I believe that serialization of television defeats the primary purpose of television - the delivery of advertising, with interesting televised segments comprising a story between. But advertisers require a consistent audience, and will abandon shows they find delivers few viewers to sell to. Neilsen ratings support the sponsor by judging a show's popularity to deliver advertising consistently.

Since advertising is sold by the network, they have an interest too in the delivery of an appealing show, including repeats, to fill out the broadcast year. The serialization format places a demand on episodes to be run in order, without which story arcs stretching over many episodes may be difficult for new viewers to delve into, so it is likely to lose its audience unless they are very dedicated to the story.

Also, if you've spent the season watching it to the end, why would you repeat watching the show and all it revealed into the off-season?

When: I believe the real transition started with the success of DALLAS. Remember, 'Who shot JR?' CBS kept an entire nation mesmerized for a summer with that question. When that happened the network powers saw that a soap (a serial) could not just survive, but thrive in 'prime time'

But network execs are notoriously slow to come around to change, even after the success of Dallas it took time for the new genre (prime time serials) to take off. Dallas gave us Knot's Landing (a spin-off), ABC Chimed in with Dynasty and networks were beginning to move toward serials...

But Why?

The advent of On Demand viewing: Before the VCR missing an episode of a serial could derail the whole viewer experience. Today I don't have to care what time the networks 'air' (or release) the show, I can watch it whenever I want to and I can take care to watch them in order. But if I had to wait for summer re-runs to catch that episode I missed, well I might as well just not bother.

Supply and Demand: In the 70's - 90's back when 'most people' had access to three networks (and PBS, and the occasional UHF channel) network time was at a premium. There was a whooping total of 63 prime-time hours available and TV execs where not prone to 'try something new' (as much as they wanted you to believe otherwise). Today the barrier to entry has gotten much lower as the distribution channels (broadcast, cable, streaming, rental, on demand) are much more wide. Each of the 'majors' (now to include Fox and others) all have 'minor leagues' they can test things in. Studios and networks are even not so tightly aligned (several ABC shows are Produced by Fox, etc). While the glut of available time slots has lead to a onslaught of trash (Kard...) even that has an audience. It's easier for a network to gamble on 'something different'. A greater population of shows to choose from has lead to a greater variety of show types. The 80's would have never seen a "Dramady" (i.e. Buffy).

Success breeds Success: As previously noted, network execs were not known to be big 'gamblers' (as in 'let's try something new and see if it sticks'). But with these new channels opening up it's easier to try something truly 'new' (Survivor... and now all these reality shows) Once something succeeds in television the networks all want to pile on and capture their piece of the action.

footnote: before Dallas there were a few exceptions, Peyton Place, etc... but their success was arguable in their day...They were critically acclaimed but still struggled for ratings.

I think many of these answers are excellent--including the chosen answer which is essentially stating "it may be more fuzzy memory" than statistical truth. I think the technology addition is good as well--both DVRs and DVD sales.

On other possible reason that we have more serial shows now than before is that we simply have a lot more TV. Cable was the big shift in the 80s but even then, TV series weren't a primary focus on a lot of the networks. Today many of the networks have morphed from their original intent into producers and developers of their own television series. Nickelodeon, Disney, AMC, MTV, Animal Planet, and dozens of others (not to mention non-networks such as Amazon and Netflix).

So we simply have a lot more TV...meaning both more serialized shows as well as more episodic based shows. Depending on your tastes, you may be drawn to the more serialized options due to the fact that they tend to put a lot of effort into story telling. Plus, going back to the technology aspect, you can binge watch them.

I have no research for this one, but my own fuzzy memory would put the start of the shift to 1978 and the first prime-time soap opera, Dallas. It began as a 5-part miniseries and grew into a serial. It's popularity took off with the 1980 season-end cliffhanger "Who shot JR?" America was hooked. It was followed by a slew of other primetime soaps, and then other shows began to serialize to pull audiences back week after week. A successful serial is an advertiser's dream!

I started to compile a list, but some clear patterns have already emerged. (Feel free to add televisions series from the years in between.)

Firmly episodic:

• Gilligan's Island (1964-1967): They don't build upon their ideas to escape the island
• Star Trek (1966-1969): The Romulan cloaking device would have been handy to keep, along with their knowledge of time travel, but they seem to forget about these technologies.
• The Brady Bunch (1969-1974): They have to keep learning how to get along, though they do seem to very slowly learn over their five years.

Firmly serial:

• 24 (2001-2010): Each episode is extremely dependent upon those before it.
• Battlestar Galactica (2004-2009): By each episode depending heavily on its predecessor, it increases the tension as the plot thickens rapidly.
• Fringe (2008-2013): Each episode uncovers new clues which build on the body of knowledge and encourages new experiments to advance their investigation.
• House of Cards (2013-): Each episode is another step in advancing Frank's power and control, building upon all that he has done before.
• Lilyhammer (2012-): Van Zandt's character learns and grows and evolves rapidly from episode to episode.