The term was invented to describe sopranos/the wire/carnivale/et al

Rome.

Was too early.

If you allow for miniseries, then something like Roots (1977) would be one of the older ones that I have seen.

Most people say The Sopranos marked the beginning of the prestige TV era, because it was the first of a cluster of high quality, high production value shows that came out around the same time. But there are some precursors that come to mind, mostly from HBO. Rome and Oz, for example.

You could make a case to go back even further with shows like NYPD Blue (90s) or even Hill Street Blues (80s) as examples of high quality TV with long, dramatic character arcs, though these shows didn’t have much in the way of contemporaries to define them as part of an era.

I’d say Twin Peaks. It’s a wonder that is was such a success, since it’s just such a weird, singular vision of two creative people, Mark Frost and David Lynch.

Twin Peaks broke the episodic TV paradigm making way for longer stories being told via this medium. It still got loads of filler, especially in the second season parts without Lynch, but Rome wasn’t built in a day (/chuckles).

@Skavau Roots, Holocaust, V… I recall “Silk Stockings” not being high quality but it was the start of cable shows.