Air Basin and County Map Boundaries

This page last reviewed January 27, 2014

California is divided geographically into air basins and counties. The State is currently divided into 15 air basins and 58 counties. Note, some of these counties are split between two or more air basins. The map below shows the current air basin boundaries and the location of the counties that lie within each air basin.

The most recent changes to the air basin boundaries were adopted by the Board in May 1996, and split the former Southeast Desert Air Basin into the Mojave Desert Air Basin and Salton Sea Air Basin. As part of this action, the Board also added the San Gorgonio Pass area to the South Coast Air Basin. These changes are reflected on the map below.

basin county

Area Designations Maps/ State and National