The city lines of Kansas City, Missouri, cross through four counties: Cass County, Clay County, Jackson County and Platte County. Of these counties, the largest by land area is Cass County.
As of 2013, the estimated population of Kansas City is 467,007. Jackson County has the highest number of people per square mile. According to 2010 United States census data, there are 1,115 people per square mile in Jackson County, 558 in Clay County, 212 in Platte County and 142.8 in Cass County.
The only county seat within Kansas City is that of Jackson County. The Jackson County seat was moved from its original location in Independence, Missouri, by then-county-judge Harry S. Truman in 1934.