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 half of Inyo Counties. Today, Los Angeles County is immensely populated but in 1850 Los Angeles County--which then included portions of today’s Orange, Riverside, and San Bernardino Counties—only had 3,530 residents. Over time boundaries were redrawn to form new counties throughout the state, bringing the total today to 58.