What episode did Newly O'Brien leave gunsmoke?

Newly O'Brien, played by actor James Arness, left "Gunsmoke" in the series' final episode, titled "The Sharecroppers," which aired on March 31, 1975. Throughout the series, Newly was a key character, but the show concluded with him transitioning to a new chapter in his life. His departure marked the end of an era for the long-running western series.