California's State Senate districts are numbered 1st through 40th, generally in north-to-south order.
The California State Senate is the upper house of the California State Legislature. The Senate has 40 members, called senators, each representing one district.
In accordance with the Article XXI of the California Constitution, senate district boundaries are redrawn every ten years based on data from the United States Census. The current boundaries were drawn in 2011 by a California Citizens Redistricting Commission. The census enumerated population of each district was within 1% of 931,349 with an average absolute deviation of 0.449%.
References
California State Senate districts Wikipedia(Text) CC BY-SA