West Marin's 60-Acre Agricultural Minimum Lot Size

Why West Marin uses such a large minimum

West Marin -- the ranching and dairy region stretching from Point Reyes Station through Nicasio, Tomales, and Chileno Valley -- has been a working agricultural landscape for well over a century, and Marin County's land-use policy has deliberately protected that character rather than allowing it to be gradually subdivided into residential ranchettes, as happened in many other coastal California counties during the late 20th century. The county's Agricultural land-use designation applies a 60-acre minimum parcel size to land in this district, commonly referenced as A-60 zoning. That figure is large by almost any California rural-zoning standard, and it is intentional: a 60-acre minimum makes it genuinely difficult to subdivide an existing ranch into smaller residential lots, keeping the land base large enough to remain economically viable as ranchland.

This isn't a nominal or rarely enforced minimum. It sits within the broader Marin Countywide Plan, which has consistently prioritized agricultural preservation in West Marin across multiple plan updates, and it works in tandem with widespread agricultural conservation easements held by organizations such as the Marin Agricultural Land Trust (MALT), which has permanently retired development rights on a substantial share of West Marin ranchland since its founding in 1980.

What this means for a buyer

1. Do not assume a parcel smaller than 60 acres in West Marin's agricultural zone is buildable as a standalone residential lot -- confirm its specific zoning designation and legal-lot-of-record status directly with Marin County Community Development Agency before relying on any listing description.
2. Many West Marin ranches also carry a recorded agricultural conservation easement (often held by the Marin Agricultural Land Trust), which restricts further subdivision and non-agricultural development independent of, and in addition to, the underlying zoning -- ask directly whether a target property is encumbered by one, since it will not always be obvious from a standard title search summary.
3. A parcel that predates the 60-acre minimum may qualify as a legal nonconforming lot, but this status has to be verified with the county rather than assumed from acreage alone.
4. Because the agricultural designation is meant to keep land in ranching or dairy use, expect any proposed non-agricultural use -- even a single additional residence -- to draw closer land-use scrutiny than it would in an ordinary rural-residential zone.