| NSNorthwestern Steel and Wire | Sterling | IL | Primary Metal Manufacturing331111 | — | ◇ UNVERIFIED |
| NTNucor Tubular Products | Bedford Park | IL | Primary Metal Manufacturing331210 | — | ◇ UNVERIFIED |
| OIOakley Industries INC | Niles | IL | Primary Metal Manufacturing331210 | — | ◇ UNVERIFIED |
| OUOdermath USA INC | Naperville | IL | Primary Metal Manufacturing331210 | — | ◇ UNVERIFIED |
| OAOlson Aluminum Castings | Rockford | IL | Primary Metal Manufacturing331524 | — | ◇ UNVERIFIED |
| OSOlympic Steel | Schaumburg | IL | Primary Metal Manufacturing331221 | — | ◇ UNVERIFIED |
| OMOutboard Marine CORP. | Waukegan | IL | Primary Metal Manufacturing331521 | — | ◇ UNVERIFIED |
| PRPechiney Rolled Products LLC | Mc Cook | IL | Primary Metal Manufacturing331315 | — | ◇ UNVERIFIED |
| PCPneu-fast CO the | Evanston | IL | Primary Metal Manufacturing331222 | 20-99 | ◇ UNVERIFIED |
| PMPrecious Metal Refining Svcs INC | Wauconda | IL | Primary Metal Manufacturing331492 | — | ◇ UNVERIFIED |
| PCPrecise Castings INC | Saint Charles | IL | Primary Metal Manufacturing331521 | — | ◇ UNVERIFIED |
| PEPrecision Extrusions LLC | Bensenville | IL | Primary Metal Manufacturing331316 | — | ◇ UNVERIFIED |
| PIPrimecast, Inc.(former) | South Beloit | IL | Primary Metal Manufacturing331511 | — | ◇ UNVERIFIED |
| RDRacer Danville Landfill | Danville | IL | Primary Metal Manufacturing331511 | — | ◇ UNVERIFIED |
| RTRepublic Technologies International LLC | Harvey | IL | Primary Metal Manufacturing331221 | — | ◇ UNVERIFIED |
| RMReserve Marine Terminal | Chicago | IL | Primary Metal Manufacturing331110 | — | ◇ UNVERIFIED |
| RWRobert White | Centralia | IL | Primary Metal Manufacturing331524 | — | ◇ UNVERIFIED |
| RSRoll Services INC | Glenwood | IL | Primary Metal Manufacturing331112 | — | ◇ UNVERIFIED |
| RTRubicon Technology | Batavia | IL | Primary Metal Manufacturing331210 | — | ◇ UNVERIFIED |
| SCSandwich Casting & Machine/trio Foundry INC | Montgomery | IL | Primary Metal Manufacturing331529 | — | ◇ UNVERIFIED |
| SISandwich Iron Foundry | Plano | IL | Primary Metal Manufacturing331511 | — | ◇ UNVERIFIED |
| SESapa Extrusions INC | Morris | IL | Primary Metal Manufacturing331316 | — | ◇ UNVERIFIED |
| SRSims Recycling Solutions | West Chicago | IL | Primary Metal Manufacturing331314 | — | ◇ UNVERIFIED |
| SLSlater Lemont CORP | Lemont | IL | Primary Metal Manufacturing331110 | — | ◇ UNVERIFIED |
| SASmall Assemblies INC | Chicago | IL | Primary Metal Manufacturing331523 | — | ◇ UNVERIFIED |
| SISpecialloy INC | Chicago | IL | Primary Metal Manufacturing331420 | — | ◇ UNVERIFIED |
| SSSterling Steel Foundry | Sauget | IL | Primary Metal Manufacturing331513 | — | ◇ UNVERIFIED |
| TOTherm O Link INC | Morris | IL | Primary Metal Manufacturing331420 | — | ◇ UNVERIFIED |
| TSThompson Steel CO INC | Franklin Park | IL | Primary Metal Manufacturing331221 | — | ◇ UNVERIFIED |
| TKTool King INC | Wheeling | IL | Primary Metal Manufacturing331511 | — | ◇ UNVERIFIED |
| TFTrio Foundry INC | Aurora | IL | Primary Metal Manufacturing331524 | — | ◇ UNVERIFIED |
| UAUnited American Metal | Chicago | IL | Primary Metal Manufacturing331420 | — | ◇ UNVERIFIED |
| UDUS Diecasting INC | Chicago | IL | Primary Metal Manufacturing331521 | — | ◇ UNVERIFIED |
| USUS Steel CORP Joliet Works | Joliet | IL | Primary Metal Manufacturing331110 | — | ◇ UNVERIFIED |
| USUS Steel - Gary Works | Chicago | IL | Primary Metal Manufacturing331110 | — | ◇ UNVERIFIED |
| VIVermilion Iron Works | Hoopeston | IL | Primary Metal Manufacturing331511 | — | ◇ UNVERIFIED |
| WFWagner Foundry INC | Chicago | IL | Primary Metal Manufacturing331529 | — | ◇ UNVERIFIED |
| WCWerner CO | Franklin Park | IL | Primary Metal Manufacturing331314 | — | ◇ UNVERIFIED |
| WIWest Irving Die INC | Sandwich | IL | Primary Metal Manufacturing331521 | — | ◇ UNVERIFIED |
| WCWirco Castings INC | New Athens | IL | Primary Metal Manufacturing331511 | — | ◇ UNVERIFIED |
| WCWoodward Controls INC | Niles | IL | Primary Metal Manufacturing331491 | — | ◇ UNVERIFIED |
| AOAallied of Illinois | Franklin Park | IL | Primary Metal Manufacturing331523 | 100-499 | ◐ LIKELY ACTIVE |
| AOAFCO Olmsted | Olmsted | IL | Primary Metal Manufacturing331318 | 20-99 | ◐ LIKELY ACTIVE |
| ASAgw Steel INC | Decatur | IL | Primary Metal Manufacturing331221 | — | ◐ LIKELY ACTIVE |
| AAntioch | Antioch | IL | Primary Metal Manufacturing331315 | 500+ | ◐ LIKELY ACTIVE |
| CCharter | Chicao | IL | Primary Metal Manufacturing331491 | 1-19 | ◐ LIKELY ACTIVE |
| CTCincinnati Tool Steel Company | Rockford | IL | Primary Metal Manufacturing331210 | 100-499 | ◐ LIKELY ACTIVE |
| CCCleveland-Cliffs - Corporate Office East Chicago - Corporate | East Chicago | IL | Primary Metal Manufacturing331110 | 100-499 | ◐ LIKELY ACTIVE |
| CCmd | Elk Grove Village | IL | Primary Metal Manufacturing331491 | 20-99 | ◐ LIKELY ACTIVE |
 Combined Metals Company LLC - Sycamore | Sycamore | IL | Primary Metal Manufacturing331222 | 20-99 | ◐ LIKELY ACTIVE |
