Los Angeles County, also known as L.A. County, officially the County of Los Angeles, is a county in the U.S. state of California. As of the 2012 U.S. Census, the county has a population of 9,962,789, making it the most populous county in the United States. Los Angeles County alone is more populous than 42 individual U.S. states. The county seat is the city of Los Angeles, the largest city in California and the second-largest city in the United States.

Los Angeles County also includes two offshore islands, San Clemente Island and Santa Catalina Island. The county is home to 88 incorporated cities and many unincorporated areas. At 4,083 square miles (10,570 km2), it is larger than the combined areas of the states of Rhode Island andDelaware.

The county is home to over a quarter of all California residents and is one of the most ethnically diverse counties in the country. It is part of the Tech Coast.

Los Angeles County was one of the original counties of California, created at the time of statehood in 1850. The county’s large area included parts of what is now Kern County, San Bernardino County, Riverside County and Orange County. These parts of the county’s territory were split to form San Bernardino County in 1853, Kern County in 1866, and Orange County in 1889. In 1893, part of San Bernardino County became Riverside County.

Los Angeles County is commonly associated with the entertainment industry; all six major film studios—Paramount Pictures, 20th Century Fox, Sony,Warner Bros., Universal Pictures, and Walt Disney Studios—are located within the county. Beyond motion picture and television program production, other major industries of Los Angeles County are international trade supported by the Port of Los Angeles and the Port of Long Beach, music recording and production, aerospace, and professional services such as law and medicine.

source: wikipedia.org & quickfacts.census.gov