West, who passed away in 2017, voiced a fictionalized version of himself - as the Mayor of Quahog - for over 100 episodes.
Announcing the new casting, "Family Guy" executive producer Richard Appel tells Entertainment Weekly, "In having a conversation about, 'How do you replace him (West)?', the universal belief was, 'He's irreplaceable.' And then the next question is, 'Do you find a new mayor?' In the world of 'Family Guy', he had an important role, and a role that was necessary for a lot of stories."
"(We thought), 'Who could be as original and unexpected and comedically fun and fresh as Adam?' Sam has a voice... made for radio, and Sam Elliott quickly became our first choice."
But Elliott initially turned the role - of himself - down.
"He just felt like he didn't want to play himself," Appel adds. "So we kicked around a bunch of ideas and then said, 'What if we refashion this as Wild West for Sam Elliott and create this new character?' And he responded very well to that idea."
Season 19 of "Family Guy" premieres on 27 September.