Atchison is a city and county seat of Atchison County, Kansas, United States, along the Missouri River. As of the 2020 census, the population of the city was 10,885. The city is named in honor of US Senator David Rice Atchison from Missouri and was the original eastern terminus of the Atchison, Topeka and Santa Fe Railway. Atchison is also the home of Benedictine College.