Johnson County (county code JO) is a county located in northeast Kansas, in the central United States. The county\'s population—the fastest growing in the state of Kansas—was 451,086 at the 2000 census, and it was estimated to be 542,737 in the year 2009,[1] making it the largest in the state. Its county seat is Olathe,[2] and its most populous city is Overland Park. Johnson County has the highest median household income in the state and 19th in the nation (as of 2000) and the nation\'s 46th highest per-capita income (as of 2005). In a study released in 2005, Johnson County had the third highest EBI (Estimated Buying Income) in the nation, meaning that Johnson Countians had the third highest amount of disposable income on average. Most of the county is suburban, being a part of the Kansas City Metropolitan Area.In 2008 CNN/Money and Money magazine ranked three cities in Johnson County on its list of the \"100 Best Cities to Live in the United States. Overland Park was ranked ninth, Olathe was ranked 11th, and Shawnee was ranked 39th. Olathe was also ranked 24th in the 2008 list of the top 25 fastest growing cities in the nation, compiled by the U.S. Census Bureau.