Marin County officials are working to expand affordable housing countywide by scaling up a model that has operated with success in West Marin: the community land trust.

Born out of the civil rights movement, C.L.T.s are nonprofits that buy properties with the intent of keeping them affordable; the trust retains ownership of the land, while residents rent or own the homes built on top of it. Marin has a handful of land trusts, but they’re…