De Soto is a city along the Kansas River, in Johnson and Leavenworth counties in the U.S. state of Kansas, and part of the Kansas City Met…De Soto is a city along the Kansas River, in Johnson and Leavenworth counties in the U.S. state of Kansas, and part of the Kansas City Metropolitan Area. As of the 2020 census, the population of the city was 6,118, and the 2021 estimate is 6,380.