21st Illinois General Assembly
The 21th Illinois General Assembly, consisting of the Illinois Senate and the Illinois House of Representatives, met from January 3, 1859, to February 24, 1859.
The 21th General Assembly was preceded by the 20th Illinois General Assembly, and was succeeded by the 22nd Illinois General Assembly.
Senate
| District | Jurisdiction represented | Image | Senator | Remarks |
| 1 | Cook County | |||
| 2 | Lake County | |||
| 3 | Ogle County | |||
| 4 | Stephenson County | |||
| 5 | Lee County | |||
| 6 | Will County | |||
| 7 | LaSalle County | |||
| 8 | Peoria County | |||
| 9 | Stark County | |||
| 10 | Fulton County | |||
| 11 | Schuyler County | |||
| 12 | Adams County | |||
| 13 | Pike County | |||
| 14 | Jersey County | |||
| 15 | Sangamon County | |||
| 16 | Macon County | |||
| 17 | Tazewell County | |||
| 18 | Coles County | |||
| 19 | Jasper County | |||
| 20 | Marion County | |||
| 21 | Madison County | |||
| 22 | St. Clair County | |||
| 23 | White County | |||
| 24 | Washington County | |||
| 25 | Johnson County |