San Diego County, California, holds the records for the largest area burned and greatest number of structures destroyed in California. This paper analyzes 102 years of fire history, population growth, and weather records from 1910 through 2012 to examine the factors that are driving the wildfire system. Annual area burned is compared with precipitation during the winter preceding the summer-fall fire season and with a five-year running average precipitation. All fires over 4 000 ha from 1950 through 2012 are examined for fuel age at the section of origin, fuel type, and weather, including the presence or absence of foehn winds. The burning characteristics between chaparral and Coastal sage scrub are examined. Annual precipitation was found to have no relationship to the annual area burned. Population increased over 50 times but mean area burned showed no statistical increase. Young chaparral (>20 years)age was shown to constrain the spread or wildfire while coastal sage scrub showed less resistance to fire at any age. Old age chaparral was significant of large wild fires.