Atchison County, Kansas

Atchison County, Kansas
Atchison County Courthouse in Atchison (2023)
Atchison County Courthouse in Atchison (2023)
Flag of Atchison County, Kansas
Official logo of Atchison County, Kansas
Map of Kansas highlighting Atchison County
Location within the U.S. state of Kansas
Country United States
State Kansas
FoundedAugust 25, 1855
Named forDavid Rice Atchison
SeatAtchison
Largest cityAtchison
Area
 • Total
434 sq mi (1,120 km2)
 • Land431 sq mi (1,120 km2)
 • Water2.6 sq mi (6.7 km2)  0.6%
Population
 (2020)
 • Total
16,348
 • Estimate 
(2025)
16,172 Decrease
 • Density37.9/sq mi (14.6/km2)
Time zoneUTC−6 (Central)
 • Summer (DST)UTC−5 (CDT)
Area code913
Congressional district2nd
WebsiteAtchisonCountyKS.org

Atchison County is a county located in the northeastern portion of the U.S. state of Kansas. Its county seat and most populous city is Atchison. As of the 2020 census, the county population was 16,348. The county was named in honor of David Atchison, a U.S. Senator from Missouri and border ruffian during the "Bleeding Kansas" era.