Gardner is a city in Johnson County, Kansas, United States. As of the 2010 census, the city population was 19,123. It is located in the Kansas City metropolitan area.
Gardner was founded where the Santa Fe Trail and the Oregon/California Trails divided. The Santa Fe Trail sent travelers southwest through Sante Fe and Albuquerque toward Los Angeles and San Diego. The Oregon/California Trails bore west for a few miles before turning north toward the Kansas River valley, followed the Big Blue River into present-day Nebraska, followed the Platte River west, and ultimately split in present-day Wyoming, Idaho or Utah.
Gardner was founded as a Free-Stater settlement in 1857. Settled primarily by emigrants from Massachusetts, it was named for Henry Gardner, then governor of Massachusetts. Four years after its establishment, it became the first community in Johnson County — and perhaps the first in the state — to experience an attack by Confederate forces.
The first post office in Gardner was established in 1858.
Gardner is located at 38°48′45″N 94°55′7″W (38.812367, -94.918621). According to the United States Census Bureau, the city has a total area of 10.21 square miles (26.44 km2), of which 10.16 square miles (26.31 km2) is land and 0.05 square miles (0.13 km2) is water.
The climate in this area is characterized by hot, humid summers and generally mild to cool winters. According to the Köppen Climate Classification system, Gardner has a humid subtropical climate, abbreviated "Cfa" on climate maps.
As of the census of 2010, there were 19,123 people, 6,644 households, and 4,938 families living in the city.