This is a list of the 100 largest counties in the United States by population. The list is based on the population estimates for July 1, 2007, the most recently released estimates from the United States Census Bureau.^[1] It is not based on an actual count of population, as the United States conducts a head count census only once every ten years, most recently in 2000. To create this estimate, the Census Bureau starts with the base number as determined during the most recent decennial census, and then estimates births, deaths, and net migration based on various sources to establish the final number.^[2]

The estimates released by the Census Bureau are not final, and are often disputed. Numerous local jurisdictions challenged their 2006 population estimate. For example, Baltimore City successfully challenged its original census estimate, resulting in a revised population estimate that moved Baltimore two places higher on the list.^[3] As of June 11, 2008, there have been no successful challenges to the 2007 estimates. In addition to challenging official Census estimates, several states perform population estimates using a different methodology than the Census Bureau. California, for example, has released population estimates that generally exceed Census figures significantly.^[4]

Many of the counties on the list include major cities or metropolitan areas. Three of the listed counties have consolidated city and county government, namely the City and County of Honolulu, City and County of Philadelphia and the City and County of San Francisco.^[5][6][7] Baltimore, Maryland is identified as a city but is considered to be a county-equivalent by the Census Bureau, and is therefore included in the list. Queens County, Kings County, New York County, and Bronx County, New York are coterminous with boroughs of New York City, fall under the jurisdiction of the combined city government, and therefore lack a county seat. Each of these counties is listed instead with the location of its county courthouse.

[edit] List of most populous counties

Downtown Los Angeles, County Seat of the most populous county in the United States, county buildings, bottom right.

Downtown Chicago, in Cook County, Illinois, the second most populous county in the United States.

Downtown Houston, located in Harris County, Texas, the third most populous county in the United States

Downtown Phoenix, Arizona, county seat of the fourth most populous county in the United States, Maricopa County, Arizona.

Aerial view of Orange County, California, the 5th most populous county in the United States.

Row houses in Brooklyn, Kings County, New York, the 7th most populous county in the United States.

Downtown Miami in Miami-Dade County, the largest county in Florida, and the county seat of the 9th most populous county in the United States.

The Guardian Building in Detroit, headquarters of Michigan's Wayne County, 13th most populous county in the United States.

Seattle seat of King County, Washington, King County ranks as the 14th most populous county in the United States.

The county government center in Las Vegas, Clark County, Nevada, 15th most populous county in the United States.

[edit] References