Caltrans Regions

The District boundary definitions are primarily based on the county boundaries. 2010 Census TIGER/Line county data were used to create this district boundary layer. Following the Census data, for the coastal counties, new District data use three-mile offshore lines instead of the coastlines that the old Caltrans District data had been used.

Two versions of District layers were created: for the islands in the Pacific Ocean, one keeps the islands the same as Census county data and another for cartography purpose does not include the islands and only shows the mainland of California.