Johnson County was created on Aug. 25, 1855, as one of the first 33 counties by the Legislative Act of 1855 in the Territory of Kansas. There now are 105 counties.

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Kansas became the 34th state in the Union on Jan. 29, 1861. Johnson County’s namesake is the Rev. Thomas Johnson, a Methodist minister, who opened the Shawnee Methodist Mission and Indian Manual Labor School in Fairway in 1839.

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The county was once part of the Shawnee Indian reservation. For generations, the area was the ancestral homelands or territory of the Osage and Kanza (Kaw) Tribes west and south of the Missouri River, as well as the Missouri(a) tribe north of the Missouri River. The Kaw and Osage tribes hunted on the county’s prairies and fished in its wooded creeks, with the Kaw maintaining seasonal communities along the Kansas (or Kaw) River.

 

Of the 20 cities in Johnson County, eight cities were incorporated before 1922. Six cities' names reflect the Native American heritage of the Shawnee tribe or the 187-year-old Indian mission. It is now a national and state historic site.

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The first trains rolled through Johnson County in 1867. Within the next decade, four railroads crossed the county, and towns sprung up nearby. A railroad could make or break a community. Some, like Edgerton, Gardner, Spring Hill, Olathe and Merriam, grew, while other small frontier rail towns faded into history.

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Johnson County played a key role in westward expansion in the United States in the 19th century. The Santa Fe, Oregon and California Trails began in Missouri, winding west before splitting off in Gardner. It's estimated at least 500,000 emigrants used the three trails to settle in western America.

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Most Johnson County cities were created in the significant suburban expansion and population boom in Johnson County in the late 1940s and early 1950s. Ten cities, mostly in northeast Johnson County, were incorporated in just four years. The county’s population between 1940 and 1960 grew from 33,000 to more than 143,000.

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The population continued to grow as Fortune 500 and 100 companies opened offices and headquarters in places like Corporate Woods, which drew national and international workers along with the county’s burgeoning hospitals and medical facilities, warehouses and research labs here in the heartland.