Answer: Dallas

Today, we’re used to the idea of television shows rocking both episode and full season cliffhangers. Historically, however, cliffhangers were really rare in American television. TV networks preferred non-serialized content because shows that had no timeline anchors could be broadcast in any order without continuity issues. If a show was about a hardened detective solving crime or a funny suburban family, it was all the better if each episode was a small story that could be digested by itself—no need to keep the episodes in order to make sense of the detective’s personal struggles or the big changes in the family.

The strong reluctance of major networks to run a show with a heavily serialized story and a cliffhanger ending changed after the incredible popularity of the 1980 third season finale of CBS’s Dallas, “A House Divided”—famously advertised as “Who Shot J.R.?” and frequently called by that name at the time. That particular episode ended with character J.R. Ewing, played by Larry Hagman, investigating a sound outside his office and getting shot twice by an unidentified assailant. Viewers saw the episode in March, but had to wait all the way until November to see the cliffhanger resolved in the fourth episode of the fourth season. (Spoiler Alert: He was shot by his scheming sister-in-law/mistress Kristin Shepard.)

The suspense surrounding the episode and the long delay captured the public’s imagination and it was the talk of the town, so to speak, all summer long. Hagman was offered £100,000 during a vacation in the United Kingdom to reveal the identity of the shooter (he admitted that neither he nor anyone else in the cast actually knew), bookies took bets as to which of the main characters was the killer, presidential candidates in the 1980 election joked about the show, and across the world, millions of people spent more than half a year guessing and consuming J.R. related media—the magazine cover shown here is the July 14, 1980 cover of People magazine showing Hagman portraying J.R. in his post-assault recovery state.

Other television networks took note and realized that serialized TV wasn’t so bad and cliffhangers really got a show good press. That moment in television history ushered in an age of frequent cliffhangers, and today, we’ve come to expect that every season of serialized TV will have at least a moderate cliffhanger to rope us into sitting down for the following season to resolve our burning curiosity.