Founded in 1855, Jefferson County is one of 105 counties in the state of Kansas. Historically, Jefferson County was one of the original 36 counties. The city of Oskaloosa is the county seat. With FIPS code of 87, Jefferson County has a population of 18,411 and area of 536 square miles (1,388 km2).
List of all cities in Jefferson County, KS alphabetically
| City/Town | Postal Code | Area Code |
| Grantville, KS | 66429 | 785 |
| Mc Louth, KS | 66054 | 913 |
| Meriden, KS | 66512 | 785 |
| Nortonville, KS | 66060 | 785 |
| Oskaloosa, KS | 66066 | 785 |
| Ozawkie, KS | 66070 | 785 |
| Perry, KS | 66073 | 785 |
| Valley Falls, KS | 66088 | 785 |
| Winchester, KS | 66097 | 913 |