Jackson County is a county located in the U.S. state of Missouri. As of 2000, the population was 654,880. The 2008 Census estimates put the population of Jackson County at 668,417. It is the second most populous county in Missouri after St. Louis County, owing mostly to the presence of Kansas City, the state's most populous city and focus city of the Kansas City Metropolitan Area. Although Independence retains its status as the original county seat, Kansas City serves as a second county seat and the center of county government.