Place it

In one of my book clubs, our theme this year is authors and stories of the Pacific Northwest. We started with a talk about the “Missoula (Montana) Mafia” from a member who lived there. Nevermind that we were liberal in our interpretation of the geography, we wanted an array of authors and topics. The project described in the LA Times is also place-based. I can imagine doing one about any region.
More than that, I wonder about the role of place in a book. How many stories had to happen where they did? When does setting become another character?

Rediscovering the lost writers of the Plains – LA Times