Question. Context: Ken Curtis (July 2, 1916 -- April 28, 1991) was an American singer and actor best known for his role as Festus Haggen on the long-running CBS western television series Gunsmoke. Although he appeared on Gunsmoke in other earlier roles, he was first cast in his iconic role in season 8 episode 13, "Us Haggens". His next appearance was with his mule, Ruth, in "Prairie Wolfer" in season 9 episode 16, which also featured Noah Beery Jr., as a villain.

Question: who was the actor that played festus in gunsmoke?
Answer. Ken Curtis
What step-by-step reasoning justifies that answer?
Reasoning: The relevant sentence in the passage is: Ken Curtis (July 2, 1916 -- April 28, 1991) was an American singer and actor best known for his role as Festus Haggen on the long-running CBS western television series Gunsmoke.