Located squarely in California's Central Valley, the counties of Stanislaus, Merced, Madera and San Benito comprise 80% of the 12th Senate Seat. The remaining portion of the district is located in Monterey County.

The city of Modesto provides the district's largest population center, followed by Salinas, Merced, Madera, Turlock, Hollister and Ceres.

Larger version of district map.