California was admitted to the Union as the 31st state on September 9, 1850. That year 27 original counties were created, with Mariposa and San Diego Counties the largest in acreage. Mariposa County, with an area of about 30,000 square miles, covered 1/5 of the state. Later it was subdivided into Tulare, Mono, Merced, Madera, Fresno, Kings, and Kern Counties. The original San Diego County included the areas that now comprise San Diego, Imperial, Riverside, San Bernardino, and