Bonanza ran for fourteen seasons. It premiered in 1959 and wrapped up in 1973. However, the show changed drastically after the sixth season. After that, Pernell Roberts, who played Adam Cartwright, left the show. Showrunners tried time and time again to replace him. However, no one could quite fill the urbane architect’s boots.
The eldest Cartwright boy soured on the show after just a couple of seasons. Roberts said that he wasn’t wired for series television. At the same time, he hated the fact that there was little growth in his character. He only stayed on with Bonanza for so long because he was under contract to do so. Lorne Greene tried to talk him into staying, knowing how much his absence would affect the show. However, nothing could keep Roberts on the Ponderosa.
Lorne Greene wasn’t the only one who knew what Pernell Roberts’ departure would mean for Bonanza. The late Dan Blocker, who played Hoss Cartwright, talked about this in a 1965 interview with Cactus Pryor.
Bonanza Star Dan Blocker on Pernell Roberts’ Departure
After discussing topics ranging from a political awakening in Hollywood to how long it took to shoot an episode of Bonanza, Cactus Pryor asked about Roberts leaving the show. Specifically, he asked if Blocker thought it would affect ratings on the show.
Blocker said that the cast and crew of Bonanza, as well as the network, were “Gambling that the effect will not be adverse enough to cause any kind of real trouble,” for the show. On the other hand, everyone behind the scenes knew that Pernell Roberts was a draw for a portion of the audience. Therefore, they knew that Roberts’ departure would be a “heavy and detrimental” loss for the series.
At the same time, the rest of the main cast of Bonanza was going to have a heavier workload.
Dan Blocker may not have been able to see it at the time but the Bonanza team was making a smart gamble. The loss of Pernell Roberts could be felt on the show. However, it didn’t make too big of an impact. The show ran for eight more seasons. What’s more, the show continued to be one of the highest-rated shows on television. In fact, Bonanza was the top-rated show for two years after he quit.
In 1970, Bonanza was the first series to be on Nielsen’s top five list for nine straight seasons. Roberts left the show in 1965. The series had such momentum that even the loss of one of its main characters couldn’t slow it down.