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 2010 census, the population was 89,322. Its county seat is Platte City. The county was organized December 31, 1838, from the Platte Purchase, named for the Platte River. (Platte is derived from the French word for a low, shallow, or intermittent stream. The Kansas City International Airport is located in the county, approximately one mile west of Interstate 29 between mile markers 12 and 15. The land for the airport was originally in an unincorporated portion of Platte County before being annexed by Platte City, and eventually Kansas City.
According to the U.S. Census Bureau, the county has a total area of 427 square miles (1,110 km), of which 420 square miles (1,100 km) is land and 6.6 square miles (17 km) (1.5%) is water. The county’s southwestern border with Kansas is formed by the Missouri River.
As of the census of 2000, there were 73,781 people, 29,278 households, and 20,231 families residing in the county. The population density was 176 people per square mile (68/km²). There were 30,902 housing units at an average density of 74 per square mile (28/km²). The racial makeup of the county was 91.45% White, 3.49% Black or African American, 0.46% Native American, 1.48% Asian, 0.20% Pacific Islander, 1.05% from other races, and 1.87% from two or more races. Approximately 3.00% of the population were Hispanic or Latino of any race. 23.4% were of German, 12.5% Irish, 12.2% American and 11.4% English ancestry.
There were 29,278 households out of which 34.10% had children under the age of 18 living with them, 57.00% were married couples living together, 8.80% had a female householder with no husband present, and 30.90% were non-families. 24.90% of all households were made up of individuals and 6.00% had someone living alone who was 65 years of age or older. The average household size was 2.49 and the average family size was 3.00.
In the county, the population was spread out with 25.80% under the age of 18, 8.30% from 18 to 24, 32.60% from 25 to 44, 24.50% from 45 to 64, and 8.80% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 98.10 males. For every 100 females age 18 and over, there were 95.50 males.
The median income for a household in the county was $55,849, and the median income for a family was $65,236. Males had a median income of $44,310 versus $31,005 for females. The per capita income for the county was $26,356. About 3.30% of families and 4.80% of the population were below the poverty line, including 5.70% of those under age 18 and 5.70% of those age 65 or over.