Johnson County is a county in the U.S. state of Kansas, along the border of the state of Missouri. Its county seat is Olathe. As of the 2020 census, the population was 609,863, the most populous county in Kansas. 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 second most populous city in the Kansas City Metropolitan Area.

This was part of the large territory of the Osage people, who occupied lands up to present-day Saint Louis, Missouri. 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 proslavery American missionary Thomas Johnson. The renowned gunfighter Wild Bill Hickok settled for a time in the county, 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, prior to the residents voting on whether slavery would be allowed in the territory. In 1862 during the American 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 the northeastern portion of the county adjacent to Kansas City, Missouri. Developer J. C. Nichols spurred the boom in 1914 when he built the Mission Hills Country Club to lure upscale residents who previously had been reluctant to move from Missouri to Kansas. Suburban development continued at a steady pace until the close of World War II.

Following the war, the pace of 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 US Supreme Court ruling in Brown v. Board of Education (1954) ruled that segregation of public schools was unconstitutional. Integration of public schools in Kansas City, Missouri, resulted in many white families leaving the inner city, resulting in increased migration to the 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 100,000 residents each decade between the 1990 census and 2010 census.

The 1952 Johnson County Courthouse was closed in 2020, then demolished in 2021. It was replaced by a seven-story courthouse in 2021 after over two years of construction. This new courthouse is the county's fourth building.

According to the United States Census Bureau, the county has a total area of 480 square miles (1,200 km), of which 473 square miles (1,230 km) is land and 6.5 square miles (17 km) (1.4%) is water.

The natural topography of the county consists of gently rolling terrain. The Kansas River forms a portion of the northwest boundary of the county. The elevation generally increases from north to south as the distance from the Kansas and Missouri rivers increases.

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. Located in northeastern Kansas, the county receives plentiful rainfall. The county 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 portion of the county and flows northward into the Kansas River at De Soto. Mill Creek begins in the central portion of the county in Olathe, flowing northward it empties into the Kansas River at Shawnee. Turkey Creek and Brush Creek each begin in northeast 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 portion of Olathe and Tomahawk Creek begins in south Overland Park. Each flows northeastward meeting in Leawood, where the stream retains the name of 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 portion of the county and 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 where they enter Hillsdale Lake before continuing into Miami County, eventually joining the Marais des Cygnes at Paola.

The county consists primarily of prairie grassland with corridors of forested areas along streams and rivers.

• Wyandotte County (north)
• Jackson County, Missouri (east)
• Cass County, Missouri (southeast)
• Miami County (south)
• Franklin County (southwest)
• Douglas County (west)
• Leavenworth County (northwest)

Historical population

Census	Pop.	Note	%±
1860	4,364		—
1870	13,684		213.6%
1880	16,853		23.2%
1890	17,385		3.2%
1900	18,104		4.1%
1910	18,288		1.0%
1920	18,314		0.1%
1930	21,179		15.6%
1940	33,327		57.4%
1950	62,783		88.4%
1960	143,792		129.0%
1970	220,073		53.0%
1980	270,269		22.8%
1990	357,048		32.1%
2000	451,086		26.3%
2010	544,179		20.6%
2020	609,863		12.1%
2023 (est.)	622,237		2.0%
U.S. Decennial Census 1790-1960 1900-1990 1990-2000 2010-2020

Johnson County (county code JO) is included in the Kansas City metropolitan area. The county has the highest median household income at $81,121 in 2017 and the highest per-capita income in Kansas, with the 19th highest median household income in 2000 and the 46th highest per-capita income in 2005. In 2010, Money magazine, in its list of the '100 Best Cities in the United States' in which to live, ranked Overland Park 7th (ranked 6th in 2006 and 9th in 2008) and Shawnee 17th (ranked 39th in 2008). In 2008 the same magazine also ranked Olathe 11th.

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 1,150 inhabitants per square mile (440/km). There were 226,571 housing units at an average density of 381 per square mile (147/km). 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, the population was spread out, with 26.3% under the age of 18, 7.60% from 18 to 24, 32.80% from 25 to 44, 22.50% from 45 to 64, and 10.9% who were 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.

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 365/km (950/sq mi). There were 181,612 housing units at an average density of 147/km (380/sq mi). 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 were 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 the population was spread out, with 27.10% under the age of 18, 7.60% from 18 to 24, 32.80% from 25 to 44, 22.50% from 45 to 64, and 10.00% who were 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.

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.

The county voted "No" on the 2022 Kansas Value Them Both Amendment, an anti-abortion ballot measure, by 68% to 32%, outpacing its support of Joe Biden during the 2020 presidential election.

Johnson County is entirely located within Kansas's 3rd congressional district, which has been represented by Democrat Sharice Davids since 2019. The two U.S. Senators from Kansas are Republicans Roger Marshall and Jerry Moran.

Johnson County has traditionally been considered a Republican stronghold. From 1920 through 2016, it voted for the GOP in every presidential election. This included the 1964 election, in which Barry Goldwater carried the county by nine points even as he lost Kansas statewide; the last time the Republicans have failed to carry the state. Earlier, it was one of the few counties where Franklin Roosevelt was shut out in all four of his campaigns, though FDR only lost the county by two votes in his 42-state landslide of 1932.

However, in 2016, Johnson County voted for Republican presidential nominee Donald Trump by less than a three-point margin, as the GOP's shift towards right-wing populism was considered a poor fit for the county's many moderate voters. In 2020, Joe Biden became the first Democrat to win Johnson County since Woodrow Wilson 104 years earlier, winning the county by an 8% margin. Biden's share of the vote was also the most ever won by a Democrat in Johnson County. The county's leftward trend was also reflected in the state's recent U.S. Senate elections in 2020 and 2022, where the Democratic candidates won the county despite losing statewide; prior to those elections, Johnson County had never gone to a Democrat in an election for either of Kansas's Senate seats.

Johnson County is home to 25 Kansas state representatives and 9 Kansas state senators. 13 out of 25 of Johnson County's representatives are Republicans, as are 6 of the county's 9 senators. Numerous Republicans from the area identify as moderates, compared to some of the more ideological hard-liners from other parts of the state. Differences between moderates and the more hard-line members can most commonly be seen on social issues, the most infamous being the numerous debates about the state's school finance formula in 2004 and 2014–2018.

The county government is administered by an elected, seven-member Board of County Commissioners, with six elected from single-member districts and one at-large. Governance of the county is divided into six districts. The county government has full jurisdiction of the unincorporated areas of the county and limited jurisdiction of those areas of the county within incorporated places. For instance, decisions regarding the regulation of land use, development and zoning in unincorporated areas of the county are the responsibility of the county government, whereas such decisions for areas within incorporated places are the jurisdiction of the incorporated city of which the property is a part.

As of 2024:

Party		District	Name
	Democratic	At-large	Mike Kelly
	Democratic	District 1	Becky Fast
	Democratic	District 2	Jeff Meyers
	Republican	District 3	Charlotte O’Hara
	Democratic	District 4	Janeé Hanzlick
	Democratic	District 5	Michael Ashcraft
	Democratic	District 6	Shirley Allenbrand

Party		Office	Name	Reference(s)
	Republican	District Attorney	Stephen Howe
	Republican	Sheriff	Calvin Hayden

The current sales tax rate in Johnson County is 7.975%, higher than the 6.5% rate in Wyandotte (where Kansas City, Kansas is located). The sales tax rates of each of the surrounding counties are nearly the same as the rate in Johnson County. Individual cities have additional sales taxes.

Property taxes are a conglomeration of state, county, city, and school district taxes. Property tax rates are generally lower in Johnson County because property values in the county are higher than in other counties throughout Kansas.

Property tax rates by city in Johnson County (2005)

City	Commercial	Real property	Motor vehicle
De Soto	3.20	1.47	3.84
Gardner	3.39	1.56	4.07
Leawood	3.39	1.56	4.07
Lenexa	2.75	1.26	3.30
Merriam	2.57	1.18	3.08
Olathe	3.09	1.42	3.71
Overland Park	2.31	1.06	2.77
Prairie Village	2.71	1.25	3.25
Shawnee	2.61	1.20	3.13

Note: Some cities have multiple tax rates because they are divided among multiple school districts. The above rates are what exist for the majority of residents in the city.

Johnson County Sheriff's Office
Patch of Johnson County Sheriff's Office
Abbreviation	JCSO
Agency overview
Formed	1861; 163 years ago (1861)
Jurisdictional structure
Operations jurisdiction	Johnson, Kansas, USA
Operational structure
Headquarters	27747 West 159th Street, New Century, KS 66031
Agency executive	Calvin Hayden (R), Sheriff
Website
Official website

The Johnson County Sheriff's Office runs the jails at Olathe and New Century, and patrols the unincorporated parts of Johnson County as well as the cities of Edgerton and DeSoto.

In 2019, the county announced that it is creating a new task force with shared jurisdiction between neighboring Miami and Franklin counties to combat crime.

In April 2024, Johnson County Sheriff Calvin Hayden claimed that he "had a search warrant in hand" when local election officials "decided in a hurry to destroy" ballots from 2019, 2020 and 2021, despite Kansas state law ordering the regular destruction of old ballots, and the local officials having informed Hayden in November 2023 that they would move to destroy the old ballots, which Hayden had asked to be preserved during his investigation of an election software firm. The local prosecutors' office said that it was "unaware of any search warrant being submitted to a judge for review". In May 2024, when Hayden was questioned on which judge approved his search warrant, Hayden responded: "there's no judge"; when the questioner replied: "A judge has to sign a search warrant to be valid", Hayden responded: "I didn’t say it was valid".

According to the 2010 Census Bureau, the education attainment of the population 25 years and over: 95.6% high school graduate or higher, 51.1% bachelor's degree or higher, and 17.9% graduate or professional degree.

The Johnson County Library has 13 branches.

School districts include:

• Blue Valley USD 229
• De Soto USD 232
• Eudora USD 491
• Gardner-Edgerton USD 231
• Olathe USD 233
• Shawnee Mission USD 512
• Spring Hill USD 230
• Wellsville USD 289

• Johnson County Community College
• University of Kansas Edwards Campus
• Kansas State University, Olathe Campus
• Kansas Christian College (Overland Park)
• MidAmerica Nazarene University
• Baker University, Overland Park Campus
• Ottawa University, Overland Park Campus
• Park University, Lenexa Campus

Johnson County has a grid network through most of the county, with a road every mile. The grid has facilitated rapid growth and easy access. Interstate 435 runs through much of the county, and serves as a developmental "border" in the northbound–southbound portion. The westbound–eastbound part of I-435 divides the county into a northern and southern section. The northern section is older, while the southern portion is the fastest-growing area in Johnson County, containing a massive volume of new homes.

The Johnson County numbered street grid generally begins at 47th Street, the Wyandotte County line (the lowest numbered street is 40th Street in Bonner Springs), and is a continuation of the adjacent Kansas City, Missouri, street grid. The grid continues to 215th Street, and into Miami County (with somewhat different named roads) to 407th Street at the Miami-Linn county line, with most suburban development ending around 167th Street. Named streets in the grid run from State Line Road (1900 West) to County Line Road (40699 West) at the Douglas County line. A portion of the grid extends north from Westwood into the Rosedale area in Kansas City, Kansas.

Another principal highway running through the area is Interstate 35, which runs diagonally through the county, entering it near Downtown Kansas City, and continuing through Olathe and Gardner. Outside the county, it eventually leads to Duluth, Minnesota in the north and the US–Mexico border in the south. U.S. 69 also serves Johnson County, entering from Wyandotte County at the south end of Interstate 635. Much of U.S. 69 within the county is freeway; this freeway eventually heads south and connects to Fort Scott and the rest of southeast Kansas.

• I-35 Southwest corner with Franklin County northeast through Edgerton, Gardner, Olathe, Lenexa, Overland Park, and Merriam to the northeast corner with downtown Kansas City
• I-435 Northern border with Wyandotte County south through Shawnee and Lenexa to K-10 then east through Overland Park and Leawood to the Missouri border
• I-635 Starts in Johnson County at I-35 and enters Wyandotte County/Kansas City, KS less than 1000 feet later.
• US-50 Southwest corner with Franklin County northeast through Edgerton, Gardner, Olathe, Lenexa, Overland Park, and Merriam to the northeast corner with downtown Kansas City
• US-56 Southwest border with Douglas County east through Edgerton and Gardner to I-35
• US-69 Southeast border with Miami County north through Stilwell and Overland Park past I-435 to I-35
• US-169 Southern border with Miami County. Joins with I-35 in Olathe.
• K-7 Southern border with Miami County north through Spring Hill, Olathe, Lenexa, and Shawnee to Wyandotte County
• K-10 Western border with Douglas County east through De Soto, Lenexa, and Olathe to I-435

Johnson County is home to three general aviation airports:

• Johnson County Executive Airport
• New Century AirCenter
• Hillside Airport

The closest airport with airline service is Kansas City International Airport in Platte County, Missouri

Johnson County Transit is the public transit operator.

List of townships / incorporated cities / unincorporated communities / extinct former communities within Johnson County.

‡ means a community has portions in an adjacent county.

Johnson County was originally divided into nine townships, two of which have since been eliminated by the annexation of all their territory into independent municipalities. All of the cities are considered governmentally independent and are excluded from the census figures for the townships. In the following table, the population center is the largest city (or cities) included in that township's population total, if it is of a significant size.

Township	FIPS	Population center	Population	Population density /km (/sq mi)	Land area km (sq mi)	Water area km (sq mi)	Water %	Geographic coordinates
Aubry	03225		5,440	43 (112)	126 (49)	0 (0)	0.31%	38°46′48″N 94°41′4″W / 38.78000°N 94.68444°W / 38.78000; -94.68444
Gardner	25450		2,143	21 (55)	102 (39)	1 (0)	0.53%	38°49′7″N 94°54′31″W / 38.81861°N 94.90861°W / 38.81861; -94.90861
Lexington	39800	De Soto	3,712	10 (25)	135 (52)	2 (1)	1.79%	38°55′0″N 95°0′13″W / 38.91667°N 95.00361°W / 38.91667; -95.00361
McCamish	43625		878	8 (20)	112 (43)	0 (0)	0.34%	38°47′22″N 94°59′48″W / 38.78944°N 94.99667°W / 38.78944; -94.99667
Mission (defunct)	-		0	0 (0)	0 (0)	0 (0)	0%	39°0′7″N 94°38′11″W / 39.00194°N 94.63639°W / 39.00194; -94.63639
Monticello (defunct)	47950		0	0 (0)	0 (0)	0 (0)	0%	39°1′59″N 94°47′57″W / 39.03306°N 94.79917°W / 39.03306; -94.79917
Olathe	52600		1,187	27 (70)	44 (17)	0 (0)	0.04%	38°54′21″N 94°49′18″W / 38.90583°N 94.82167°W / 38.90583; -94.82167
Oxford	53825		2,020	121 (313)	17 (6)	0 (0)	1.54%	38°49′58″N 94°40′54″W / 38.83278°N 94.68167°W / 38.83278; -94.68167
Shawnee (defunct)	64525		0	0 (0)	0 (0)	0 (0)	0%	39°1′51″N 94°47′47″W / 39.03083°N 94.79639°W / 39.03083; -94.79639
Spring Hill	67650		2,059	29 (76)	70 (27)	0 (0)	0.30%	38°46′35″N 94°48′55″W / 38.77639°N 94.81528°W / 38.77639; -94.81528
Sources: "Census 2000 U.S. Gazetteer Files". U.S. Census Bureau, Geography Division. Archived from the original on August 2, 2002.Kansas Historical Society, Johnson County. Retrieved from the website on June 11, 2021.

• The ABC apocalyptic drama film The Day After was partially filmed in De Soto.
• Mission Hills is the setting for The ABC Family show Switched at Birth.
• Netflix original documentary Dirty Money, season 1 episode 2, entitled "Payday", features the infamous predatory loan practices of Scott Tucker, a resident of Leawood. The episode features numerous aerial views of the area.
• The indie film All Creatures Here Below is partially set in De Soto, and filmed in Kansas City.

• National Register of Historic Places listings in Johnson County, Kansas

Community information for Kansas

• Kansas locations by per capita income
• List of counties in Kansas
• List of townships in Kansas
• List of cities in Kansas
• List of unincorporated communities in Kansas
• List of ghost towns in Kansas

• History of Johnson County, Kansas; Ed Blair; 469 pages; 1915.
• Standard Atlas of Johnson County, Kansas; Geo. A. Ogle & Co; 78 pages; 1922.
• Standard Atlas of Johnson County, Kansas; Geo. A. Ogle & Co; 51 pages; 1902.
• Atlas Map of Johnson County, Kansas; E.F. Heisler; 86 pages; 1874.

County

• Johnson County - Official
• Johnson County - Directory of Public Officials

Historical

• Johnson County History

Maps

• Johnson County Maps: Current, Historic, KDOT
• Kansas Highway Maps: Current, Historic, KDOT
• Kansas Railroad Maps: Current, 1996, 1915, KDOT and Kansas Historical Society