Northwest Passage had first been adapted by MGM as a feature film starring Spencer Tracy & Walter Brennan in 1940. The studio went back to the Kenneth Edwards novel 18 years later, with future icon Buddy Ebsen, fresh from Disney's adaptation of Davy Crockett, taking over for Brennan, who was starring on The Real McCoys.
Unfortunately, Northwest Passage lasted just one season. Producer Adrian Samish is better known for his years working for Quinn Martin. Associate director Robert Justman (billed here as Bob Justman) later worked on Star Trek, among others.
Let's take a look at a sample episode, "The Assassin", with Pernell Roberts, a year before Bonanza:
Edit, 9/7/2020: Had to change the video. This copy starts from the beginning anew around the 25 minute mark: