In the pilot for the series, by Sam Peckinpah (originally written for Gunsmoke (1955) but turned down for that show), Chuck Connors' character was named John McCain, not Lucas McCain, and he didn't have a son. It was Producer Arnold Laven's idea to make McCain a widower with a son. Also, McCain was originally supposed to have been a dead shot with a pistol. Laven had the idea to use a customized Winchester rifle as McCain's weapon of choice.
Chuck Connors initially turned down the role of Lucas McCain because he thought the salary was too low. The show's producers then considered James Whitmore and John Anderson for the role, but when they saw Connors' chemistry with child actor Tommy Kirk in Old Yeller (1957), they realized he was the best choice for the role and made him another offer, this time at a much higher salary. He accepted.
In some of the episodes, note that Lucas McCain (without any connection or relevance to the plot) will handle and fire his rifle with equal precision, sometimes with his right hand, and other times with his left hand. An explanation has never been given for this ambidextrous ability.
Johnny Crawford (Mark McCain) played a Sheriff on The Big Valley (1965). An interesting symbolic act occurred when he handed a rifle to an outlaw posing as a returned Sheriff. It was a reminder of the significance of what appears to be a rifle similar to one that his father, Lucas McCain, from this show, used to much success.
John Anderson holds the record for the most appearances as a unique character with eleven appearances, usually as a heavy. In the second season, two of his appearances were back-to-back in season two, episode fifteen, "Day of the Hunter" and season two, episode sixteen, Mail Order Groom". Although he was younger than Chuck Connors, in his final role, he played Lucas' father-in-law. John Milford came in second with ten unique roles. Although he also appeared eleven times, he appeared twice as the same character.