
Sumner County
- State:
- Kansas
- County Seat:
- Wellington
Sumner County's estimated 2025 population is 22,284 with a growth rate of -0.11% in the past year according to the most recent United States census data. Sumner County is the 25th largest county in Kansas. The 2010 population was 24,119 and has seen a growth of -7.61% since that time.