Platte County is a county located in the northwestern portion of the U.S. state of Missouri and is part of the Kansas City metropolitan area. As of the 2020 census, the population was 106,718. Its county seat is Platte City. The county was organized December 31, 1838, from the Platte Purchase, named for the Platte River. The Kansas City International Airport is located in the county, approximately one mile west of Interstate 29 between mile markers 12 and 15.