Orange County is a county in the U.S. state of California. Its county seat is Santa Ana. As of the 2012 census, its population was 3,090,132, making it the third most populous county in California, behind Los Angeles County and San Diego County. It’s also the second most populous county in the Greater Los Angeles Area, after Los Angeles County. It is the sixth most populous county in the United States as of 2009 and the smallest county in Southern California by area. It’s roughly half the size of Ventura County, Southern California’s next smallest county. It is the second most densely populated county in the state, second only to San Francisco County. The county is famous for its tourism as the home of attractions like Disneyland, Knott’s Berry Farm, and several beaches along its more than 40 miles (64 km) of coastline. It is known for its political conservatism — a 2005 academic study listed three Orange County cities as among America’s 25 most conservative, making it one of two counties in the nation containing more than one such city. (Maricopa County, Arizona also has three cities on the list.) It is part of the Tech Coast.
Whereas most population centers in the United States tend to be identified by a major city, there is no defined urban center in Orange County. It is sometimes considered part of both the Los Angeles and San Diego metro areas. It is mostly suburban except for some traditionally urban areas at the centers of the older cities of Anaheim, Fullerton, Huntington Beach, Orange, andSanta Ana. There are several edge city-style developments such as Irvine Business Center,Newport Center, and South Coast Metro.
The city of Santa Ana serves as the county seat, Anaheim as its main tourist destination, andIrvine as its major business and financial hub. All of these three Orange County cities have populations exceeding 200,000. Thirty-four incorporated cities are located in Orange County; the newest is Aliso Viejo, which was incorporated in 2001. Anaheim was the first city incorporated in Orange County. It was incorporated in 1870, when the region was still part of neighboring Los Angeles County.
source: wikipedia.org & quickfacts.census.gov