| CICasting Impregnators INC | Franklin Park | IL | Fabricated Metal Product Manufacturing332812 | — | ◇ UNVERIFIED |
| CICastle-printech INC | Dekalb | IL | Printing and Related Support Activities323111 | — | ◇ UNVERIFIED |
| CICastrol Industrial North America INC | North Aurora | IL | Petroleum and Coal Products Manufacturing324191 | — | ◇ UNVERIFIED |
 Cast Technologies INC. | Peoria | IL | Primary Metal Manufacturing331524 | — | ◇ UNVERIFIED |
| CICaterpillar INC | Peoria | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CICaterpillar INC | Mossville | IL | Machinery Manufacturing333120 | — | ◇ UNVERIFIED |
| CICaterpillar INC | Peoria | IL | Plastics and Rubber Products Manufacturing326291 | — | ◇ UNVERIFIED |
| CICaterpillar INC | Peoria | IL | Machinery Manufacturing333120 | — | ◇ UNVERIFIED |
| CICaterpillar INC | Pontiac | IL | Machinery Manufacturing333618 | — | ◇ UNVERIFIED |
| CICaterpillar INC Facility H | Chillicothe | IL | Plastics and Rubber Products Manufacturing326291 | — | ◇ UNVERIFIED |
| CICaterpillar INC - Mossville Facility | Mossville | IL | Plastics and Rubber Products Manufacturing326199 | — | ◇ UNVERIFIED |
| CICaterpillar Inc- Peoria Proving Ground | East Peoria | IL | Machinery Manufacturing333120 | — | ◇ UNVERIFIED |
| CCCatty CORP | Huntley | IL | Paper Manufacturing322221 | — | ◇ UNVERIFIED |
| CSCbi Services INC | Bourbonnais | IL | Fabricated Metal Product Manufacturing332313 | — | ◇ UNVERIFIED |
| CCCedar Concepts INC | Chicago | IL | Chemical Manufacturing325611 | — | ◇ UNVERIFIED |
| CSCedar Siding & Lumber INC | Rochelle | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CLCelanese Ltd-meredosia Facility | Meredosia | IL | Chemical Manufacturing325211 | — | ◇ UNVERIFIED |
| CCCelta Chemical | Granite City | IL | Chemical Manufacturing325998 | — | ◇ UNVERIFIED |
| CDCentral Die Casting | Chicago | IL | Primary Metal Manufacturing331521 | — | ◇ UNVERIFIED |
| CICentral Illinois Ag | Farmer City | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CICentral Il Mfg CO | Bement | IL | Transportation Equipment Manufacturing336399 | — | ◇ UNVERIFIED |
| CMCentral Machine Shop | Pinckneyville | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CSCentral Steel & Wire CO | Chicago | IL | Primary Metal Manufacturing331210 | — | ◇ UNVERIFIED |
| CTCentury Tool & Mfg CO | Cherry Valley | IL | Fabricated Metal Product Manufacturing332111 | — | ◇ UNVERIFIED |
 Cenveo Worldwide LTD | Chicago | IL | Paper Manufacturing322230 | — | ◇ UNVERIFIED |
| CPCeramic Powders INC | Joliet | IL | Fabricated Metal Product Manufacturing332618 | — | ◇ UNVERIFIED |
| CECertified Equip & Mfg CO | Springfield | IL | Primary Metal Manufacturing331221 | — | ◇ UNVERIFIED |
| CPCertified Packaging CORP | North Chicago | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CTCertified Tool & Mfg | Elk Grove Village | IL | Fabricated Metal Product Manufacturing332116 | — | ◇ UNVERIFIED |
| CNCfc - Northern Bank Note CO | Countryside | IL | Printing and Related Support Activities323111 | — | ◇ UNVERIFIED |
| CICf Industries, INC. - Peru Terminal | Peru | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CICf Industries Sales - Seneca Terminal | Seneca | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CHCfm Harris Systems INC | Lincolnwood | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CHCfm Harris Systems INC | Skokie | IL | Fabricated Metal Product Manufacturing332510 | — | ◇ UNVERIFIED |
| CAChampaign Asphalt CO LLC | Champaign | IL | Petroleum and Coal Products Manufacturing324121 | — | ◇ UNVERIFIED |
| CBChampaign Builders Supply CO | Champaign | IL | Nonmetallic Mineral Product Manufacturing327390 | — | ◇ UNVERIFIED |
| CPChampaign Park District | Champaign | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CEChampion Environmental Services INC | St Charles | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CLChampion Laboratories INC | West Salem | IL | Transportation Equipment Manufacturing336399 | — | ◇ UNVERIFIED |
| CSChampion Specialized Products | Glendale Heights | IL | Printing and Related Support Activities323111 | — | ◇ UNVERIFIED |
| CLChampionx LLC | Mt Carmel | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CICharnor, INC. | Milan | IL | Machinery Manufacturing333924 | 20-99 | ◇ UNVERIFIED |
| CLChds LLC | Round Lake | IL | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| CLChem-cast LTD | Danville | IL | Fabricated Metal Product Manufacturing332997 | — | ◇ UNVERIFIED |
| CIChem-plate Industries INC | Maywood | IL | Fabricated Metal Product Manufacturing332813 | — | ◇ UNVERIFIED |
 Chem Processing | Rockford | IL | Fabricated Metal Product Manufacturing332813 | — | ◇ UNVERIFIED |
| CIChemstream INC Midwest Branch | West Frankfort | IL | Chemical Manufacturing325998 | — | ◇ UNVERIFIED |
| CIChemtool INC | Crystal Lake | IL | Petroleum and Coal Products Manufacturing324191 | — | ◇ UNVERIFIED |
| CAChemtura Agrosolutions -trace Chemicals | Pekin | IL | Chemical Manufacturing325320 | — | ◇ UNVERIFIED |
| CChep/ifco | Romeoville | IL | Wood Product Manufacturing321920 | — | ◇ UNVERIFIED |
