Johnson County is a county in the U.S. state of Kansas along the state's eastern border with Missouri. Its county seat is Olathe. As of the 2020 census, its population was 609,863, making it Kansas's most populous county. The county was named after Thomas Johnson, a Methodist missionary who was one of the state's first settlers. Largely suburban, the county contains a number of suburbs of Kansas City, Missouri, including Overland Park, a principal city of and the second-most populous city in the Kansas City Metropolitan Area.
History
Present-day Johnson County was part of a large territory of the Osage people, who occupied lands as far east as present-day St. Louis. After the Indian Removal, the United States government reserved much of this area as Indian territory for a reservation for the Shawnee people, who were relocated from east of the Mississippi River in the upper Midwest.
The Santa Fe Trail and Oregon–California Trail, which pass through nearby Independence, Missouri, also passed through the county. Johnson County was established in 1855 as one of the first counties in the newly organized Kansas Territory; it was named for the proslavery missionary Thomas Johnson. The renowned gunfighter Wild Bill Hickok settled in the county for a time, becoming constable of Monticello Township in 1858.
Johnson County was the site of many battles between abolitionists and pro-slavery advocates during the period of Bleeding Kansas, before residents voted on whether to allow slavery in the territory. In 1862, during the Civil War, Confederate guerrillas from nearby Missouri, led by William Quantrill, raided the Johnson County communities of Olathe and Spring Hill. They killed half a dozen men and destroyed numerous homes and businesses.
The county was largely rural until the early 20th century, when housing subdivisions were developed in its northeastern portion, adjacent to Kansas City, Missouri. Developer J. C. Nichols spurred the boom in 1914 when he built the Mission Hills Country Club to attract upscale residents who previously had been reluctant to move to Kansas. Suburban development continued at a steady pace until the close of World War II.
After the war, development exploded, triggered by the return of veterans in need of housing, construction of highways that facilitated commuting from suburbs, and the pent-up demand for new housing. The 1954 US Supreme Court decision in Brown v. Board of Education held that segregation of public schools was unconstitutional. Integration of public schools in Kansas City, Missouri, led many white families to leave the inner city, resulting in increased migration to Johnson County for new housing and what were considered higher-quality public schools, generally an indicator of higher economic status. From the mid-1980s, the pace of growth increased significantly, with the county adding 200,000 residents between the 1990 and 2010 censuses.
The 1952 Johnson County Courthouse closed in 2020 and was demolished in 2021. It was replaced by a seven-story courthouse, the county's fourth such building.
Geography
According to the United States Census Bureau, the county has an area of , of which is land and (1.4%) is water.
Topography Johnson County's natural topography consists of gently rolling terrain. The Kansas River forms part of the county's northwestern boundary. The elevation generally increases from north to south as the distance from the Kansas and Missouri rivers increases.
Watersheds and streams The county is drained by the watersheds of the Kansas, Blue, and Marais des Cygnes, all of which are part of the Missouri River watershed. The county receives plentiful rainfall. It contains numerous small streams, including Kill Creek, Mill Creek, Turkey Creek, Indian Creek, Brush Creek, Tomahawk Creek, the Blue River, Bull Creek and Little Bull Creek.
Kill Creek begins in the southwest of the county and flows northward into the Kansas River at De Soto. Mill Creek begins in the central part of the county in Olathe, flowing northward to empty into the Kansas River at Shawnee. Turkey Creek and Brush Creek each begin in northeastern Johnson County. Turkey Creek flows northeastward into Wyandotte County and joins the Kansas River just before its confluence with the Missouri River at Kaw Point. Brush Creek flows east-northeastward through Prairie Village and Mission Hills, entering Kansas City, Missouri, within the median of Ward Parkway and passing the Country Club Plaza before emptying into the Blue River east of the Country Club Plaza and north of Swope Park. Indian Creek begins in the southern part of Olathe and Tomahawk Creek begins in southern Overland Park. Each flows northeastward meeting in Leawood, where the stream retains the name Indian Creek, just before crossing the state line and entering the Blue River in Kansas City, Missouri. The Blue River begins in rural southern Johnson County and flows north-northeastward through the southeastern part of the county, crossing the state line just east of the intersection of 151st Street and Kenneth Road in southern Overland Park. The Blue River flows through southern and eastern Kansas City before joining the Missouri River. Bull Creek and Little Bull Creek begin in rural southwestern Johnson County and flow southward, entering Hillsdale Lake before continuing into Franklin County and joining the Marais des Cygnes at Paola.
Flora and fauna The county consists primarily of prairie grassland, with corridors of forested areas along streams and rivers.
Adjacent counties Wyandotte County (north) Jackson County, Missouri (east) Cass County, Missouri (southeast) Miami County (south) Franklin County (southwest) Douglas County (west) Leavenworth County (northwest)
Demographics
Johnson County (county code JO) is included in the Kansas City metropolitan area. The county has Kansas's highest median household income at $107,261 in 2019-2023 and its highest per-capita income, with the 19th-highest median household income in 2000 and the 46th highest per-capita income in 2005. 56.9 percent of residents had bachelor's degree or higher as of 2023.
Racial and ethnic composition +Johnson County, Kansas – Racial and ethnic compositionRace / Ethnicity (NH = Non-Hispanic)Pop 1980 Pop 1990Pop 2000Pop 2010 Pop 2020% 1980% 1990% 2000% 2010% 2020White alone (NH)259,663334,167401,428446,044460,39996.08%94.12%88.99%81.97%75.49%Black or African American alone (NH)3,1366,80911,56823,02828,0921.16%1.92%2.56%4.23%4.61%Native American or Alaska Native alone (NH)6761,1601,3121,6391,5950.25%0.33%0.29%0.30%0.26%Asian alone (NH)2,1185,73912,69722,59832,8560.78%1.62%2.81%4.15%5.39%Native Hawaiian or Pacific Islander alone (NH)x included in the Asian category in the 1980 Censusx included in the Asian category in the 1990 Census149259346xx0.03%0.05%0.06%Other race alone (NH)6411744598642,3930.24%0.05%0.10%0.16%0.39%Mixed race or Multiracial (NH)x not an option in the 1980 Censusx not an option in the 1990 Census5,51610,79829,793xx1.22%1.98%4.89%Hispanic or Latino (any race)4,0357,00517,95738,94954,3891.49%1.97%3.98%7.16%8.92%Total270,269355,054451,086544,179609,863 100.00%100.00%100.00%100.00%100.00%
2020 census
As of the 2020 census, the county had a population of 609,863. The median age was 38.2 years. 24.2% of residents were under the age of 18 and 15.6% of residents were 65 years of age or older. For every 100 females there were 95.9 males, and for every 100 females age 18 and over there were 93.4 males age 18 and over. 96.0% of residents lived in urban areas, while 4.0% lived in rural areas.
The racial makeup of the county was 77.6% White, 4.7% Black or African American, 0.4% American Indian and Alaska Native, 5.4% Asian, 0.1% Native Hawaiian and Pacific Islander, 3.1% from some other race, and 8.7% from two or more races. Hispanic or Latino residents of any race comprised 8.9% of the population.
There were 239,492 households in the county, of which 32.7% had children under the age of 18 living with them and 23.9% had a female householder with no spouse or partner present. About 26.2% of all households were made up of individuals and 9.7% had someone living alone who was 65 years of age or older.
There were 251,681 housing units, of which 4.8% were vacant. Among occupied housing units, 67.4% were owner-occupied and 32.6% were renter-occupied. The homeowner vacancy rate was 1.2% and the rental vacancy rate was 7.5%.
2010 census As of the 2010 census, there were 544,179 people, 210,278 households, and 143,509 families residing in the county. The population density was . There were 226,571 housing units at an average density of . The racial makeup of the county was 86.0% White, 4.2% Asian, 4.3% Black or African American, 0.4% Native American, 0.01% Pacific Islander, 1.55% from other races, and 2.5% from two or more races. Hispanic or Latino of any race were 7.2% of the population. 30.6% identified as of German, 16.8% Irish, 13.6% English and 5.7% American ancestry.
There were 210,278 households, out of which 34.6% had children under the age of 18 living with them, 56.1% were married couples living together, 8.4% had a female householder with no husband present, and 31.8% were non-families. 25.9% of all households were made up of individuals, and 7.8% had someone living alone who was 65 years of age or older. The average household size was 2.51 and the average family size was 3.05.
In the county, 26.3% of the population was under the age of 18, 7.60% was from 18 to 24, 32.80% from 25 to 44, 22.50% from 45 to 64, and 10.9% was 65 years of age or older. The median age was 36.4 years. 48.8% of the population were males and 51.2% of the population were females.
The median income for a household in the county was $73,733, and the median income for a family was $90,380. Males had a median income of $61,346 versus $43,785 for females. The per capita income for the county was $37,882. About 3.6% of families and 5.5% of the population were below the poverty line, including 7.1% of those under age 18 and 4.9% of those age 65 or over.
2000 census As of the census of 2000, there were 451,086 people, 174,570 households, and 121,675 families residing in the county. The population density was . There were 181,612 housing units at an average density of . The racial makeup of the county was 91.11% White, 2.61% Black or African American, 0.33% Native American, 2.83% Asian, 0.03% Pacific Islander, 1.55% from other races, and 1.54% from two or more races. 3.98% of the population was Hispanic or Latino of any race.
There were 174,570 households, out of which 36.00% had children under the age of 18 living with them, 59.20% were married couples living together, 7.80% had a female householder with no husband present, and 30.30% were non-families. 24.50% of all households were made up of individuals, and 6.70% had someone living alone who was 65 years of age or older. The average household size was 2.56 and the average family size was 3.09.
In the county, 27.10% of the population was under the age of 18, 7.60% was from 18 to 24, 32.80% from 25 to 44, 22.50% from 45 to 64, and 10.00% was 65 years of age or older. The median age was 35 years. For every 100 females there were 95.50 males. For every 100 females age 18 and over, there were 92.00 males.
The median income for a household in the county was $61,455, and the median income for a family was $72,987. Males had a median income of $49,790 versus $32,145 for females. The per capita income for the county was $30,919. 3.40% of the population and 2.10% of families were below the poverty line. Out of the total population, 3.30% of those under the age of 18 and 3.60% of those 65 and older were living below the poverty line.
Government
Laws Johnson County was a prohibition, or "dry", county until the Kansas Constitution was amended in 1986 and voters approved the sale of alcoholic liquor by the individual drink, with a 30% food sales requirement.