Los Angeles County, one of California’s original 27 counties, was established Feb. 18, 1850. Originally the County occupied a comparatively small area along the coast between Santa Barbara and San Diego, but within a year its boundaries were enlarged from 4,340 square miles to 34,520 square miles, an area sprawling east to the Colorado River.

During subsequent years, Los Angeles County slowly ebbed to its present size, the last major detachment occurring in 1889 with the creation of Orange County. Los Angeles County remains one of the nation’s largest counties with 4,084 square miles, an area some 800 square miles larger than the combined area of the states of Delaware and Rhode Island.

Los Angeles County includes the islands of San Clemente and Santa Catalina. It is bordered on the east by Orange and San Bernardino Counties, on the north by Kern County, on the west by Ventura County, and on the south by the Pacific Ocean. Its mainland coastline is 75 miles long.

Los Angeles County has the largest population (10,441,080 as of January 2010) of any county in the nation, and is exceeded by only eight states. Approximately 27 percent of California’s residents live in Los Angeles County. The Board of Supervisors, created by the state Legislature in 1852, is the governing body. Five supervisors are elected to four-year terms by voters within their respective districts. The Board has executive, legislative and quasi-judicial roles. It appoints all department heads other than the assessor, district attorney and sheriff, which are elective positions. The Board has delegated its role in selecting all but a few of the department heads to the chief executive officer, but still must approve appointments. As a subdivision of the state, the County is charged with providing numerous services that affect the lives of all residents. Traditional mandatory services include law enforcement, property assessment, tax collection, public health protection, public social services and relief to indigents. Among the specialized services are flood control, water conservation, parks and recreation, and many diversified cultural activities.

There are 88 cities within the County, each with its own city council. All of the cities, in varying degrees,contract with the County to provide municipal services. Thirty-seven contract for nearly all of their municipal services.

More than 65 percent of the County – 2,649 square miles – is unincorporated. For the 1 million people living in those areas, the Board of Supervisors is their "city council" and County departments provide the municipal services. The County's budget is over $25 billion. 22 percent of the revenue comes from the state, 22 percent from the federal government, 19 percent from property taxes, and 37 percent from other sources. The largest percent of the budget, 27 percent, goes to pay for health services, while 26 percent is spent on public protection and 26 percent on social services.

The County, with 101,296 budgeted positions, is the largest employer in the five-county region. Of these budgeted positions, 31,568 are in law and justice, 28,772 are in health services, and 21,405 are in social services. The spectrum of job listings – from clerk to truck driver, sanitarian to psychiatrist, scientist to scuba diver, attorney to helicopter pilot – encompasses nearly every trade and profession, and illustrates the complexity of County government.