Yorkville is a city located in Kendall County, Illinois, United States. The population was 6,189 at the 2000 United States Census and is estimated to be 16,505, as of the 1 July 2008, Census Bureau statistics. It is the county seat of Kendall County. Yorkville is located in the center of Kendall County, the fastest growing county in Illinois and according to recent statistics released in March, 2009, by the U.S. Census Bureau, is the fourth fastest growing county in the United States.