Every ten years, supervisorial districts must be redrawn so that each district is substantially equal in population. This process, called redistricting, is important in ensuring that each Board of Supervisors member represents about the same number of constituents. As many of the districts have changed boundaries, the newly adopted district maps can be viewed at this link.

The Fourth District encompasses Nipomo, Arroyo Grande, Huasna, Edna Valley, California Valley, and unincorporated portions of San Luis Obispo.

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