Largest Employers – Southwestern Illinois
| Company | County | Employees | Source |
| Scott Air Force Base | St. Clair County | 13,000 | 6 |
| Amazon Inc. | Madison County | 4,100 | 6 |
| Southern Illinois University Edwardsville | Madison County | 3,500 | 6 |
| Hospital Sisters Health System | St. Clair County | 2,350 | 3 |
| Southwestern Illinois College | St. Clair County | 1,403 | 5 |
| U.S. Steel | Madison County | 1,200 | 5 |
| Southwestern Illinois Health Facilities Inc. | Madison County | 1,190 | 6 |
| Wieland Rolled Products (formerly Olin Brass) | Madison County | 1,118 | 9 |
| Philips 66 Wood River Refinery | Madison County | 1,100 | 2 |
| Alton Memorial Hospital | Madison County | 1,017 | 9 |
| Madison County | Madison County | 984 | 2 |
| Gateway Regional Medical Center | Madison County | 955 | 6 |
| East St. Louis School District | St. Clair County | 950 | 2 |
| Edwardsville Community Unit School District #7 | Madison County | 922 | 6 |
| St. Clair County | St. Clair County | 850 | 5 |
| ASF Keystone | Madison County | 830 | 5 |
| Alton Community Unit School District #11 | Madison County | 806 | 9 |
| Basler Electric Co. | Madison County | 800 | 5 |
| Catholic Diocese of Belleville | Madison County | 800 | 3 |
| Park Fairmount Inc | Madison County | 800 | 8 |
| GEODIS | Madison County | 750 | 1 |
| SSM Health St. Anthony | Madison County | 733 | 9 |
| Army & Air Force Exchange Svc | St. Clair County | 730 | 1 |
| Gmri Inc – Red Lobster | St. Clair County | 730 | 1 |
| Allsup Inc. | St. Clair County | 700 | 6 |
| Belleville Public School District #118 | St. Clair County | 700 | 3 |
| FKG Oil Company | Madison County | 700 | 3 |
| Lanter Transport Inc. | St. Clair County | 700 | 3 |
| O’Fallon Community Consolidated School District #90 | St. Clair County | 680 | 2 |
| SIHF Healthcare | St. Clair County | 664 | 6 |
| Granite City Community Unit School District #9 | Madison County | 650 | 5 |
| Casino Queen Hotel and Casino | St. Clair County | 647 | 6 |
| Lewis & Clark Community College | Madison County | 641 | 6 |
| Amsted Rail | Madison County | 637 | 7 |
| Cahokia School District #187 | St. Clair County | 637 | 6 |
| Woolpert | St. Clair County | 622 | 6 |
| Penn National Gaming- Alton | Madison County | 570 | 6 |
| GRP Mechanical Co. Inc. | Madison County | 565 | 6 |
| Owens-Brockway Machinery Manufacturing Plant | Madison County | 550 | 3 |
| Triad Community School District | Madison County | 543 | 5 |
| West Star Aviation | Madison County | 540 | 6 |
| Henderson Trucking | St. Clair County | 530 | 6 |
| Rockwood Pigments NA Inc | St. Clair County | 515 | 8 |
| Southern Illinois Healthcare Foundation | St. Clair County | 512 | 6 |
| Alton Square | Madison County | 500 | 3 |
| Belleville Shoe | St. Clair County | 500 | 6 |
| Cerro Flow Products Inc. | St. Clair County | 500 | 3 |
| Glik Stores | Madison County | 500 | 3 |
| Mascoutah Community School | St. Clair County | 500 | 1 |
Sources:
(1) “Selectory” Dun & Bradstreet, www.selectory.com.
(2) Information from organization.
(3) “Sorkins Directory” Sorkins, www.sorkins.com.
(4) “ReferenceUSA” InfoUSA, www.referenceusa.com.
(5) St. Louis Regional Chamber internal sources.
(6) St. Louis Business Journal
(7) St. Louis Post-Dispatch
(8) “Hoovers” Dun & Bradstreet, www.hoovers.com
(9) Internet, other