While not the lowest-rated "Doctor Who" story of all time, or even the lowest-rated Hartnell story, "The Gunfighters" did open a sustained period of significantly lower ratings for the program that lasted almost the entirety of the remainder of the First Doctor's era. Beginning with "The O.K. Corral" — the very same episode that received the lowest Audience Appreciation figures of any "Doctor Who" episode — no Hartnell episode topped 6 million viewers until Episode 2 of his final story, "The Tenth Planet".