| NSNucor Skyline | Armorel | AR | — | ◇ UNVERIFIED |
| NTNucor Towers and Structures | New Ross | IN | — | ◇ UNVERIFIED |
| NTNucor Towers & Structures | Crawfordsville | IN | — | ◇ UNVERIFIED |
| NVNucor Vulcraft Group | San Antonio | TX | — | ◇ UNVERIFIED |
| NVNucor Vulcraft - St. Joe Division | Saint Joe | IN | — | ◇ UNVERIFIED |
| NNucraft | Roscommon | MI | — | ◇ UNVERIFIED |
| NSNuEra Steel LLC | Viborg | SD | — | ◇ UNVERIFIED |
| NCNueva Castilla Iron Works, INC. | San Francisco | CA | — | ◇ UNVERIFIED |
| NRNufab Rebar-slidell, LLC | Alexandria | LA | — | ◇ UNVERIFIED |
| NNNumber Nine, L.l.c. | Lk Havasu Cty | AZ | — | ◇ UNVERIFIED |
| NFNusteel Fabricators, INC. | Childersburg | AL | — | ◇ UNVERIFIED |
| NSNWA Steel Co LLC | Siloam Springs | AR | — | ◇ UNVERIFIED |
| NINw Iron Works INC | Portland | OR | — | ◇ UNVERIFIED |
| OIOakdale Iron Works, INC. | Oakdale | PA | — | ◇ UNVERIFIED |
| OFOberlin Filter Company | Pewaukee | WI | — | ◇ UNVERIFIED |
| OCObie Construction, INC. | Eugene | OR | — | ◇ UNVERIFIED |
| OMO'Brien Metal Inc. | Chicago | IL | — | ◇ UNVERIFIED |
| OOO'brien Oilfield Services, LLC | Belfield | ND | — | ◇ UNVERIFIED |
| OOObrien Ornamental Iron INC | Minneapolis | MN | — | ◇ UNVERIFIED |
| OIOcci INC. Wwtp | Fulton | MO | — | ◇ UNVERIFIED |
 Occupational Development Center INC Dba Custom Pro | Bemidji | MN | — | ◇ UNVERIFIED |
| OSOcean Steel Corporation | Binghamton | NY | — | ◇ UNVERIFIED |
| OCOctober CO Chemetal Division | Easthampton | MA | — | ◇ UNVERIFIED |
| OIOdom Industries, INC | Milford | OH | — | ◇ UNVERIFIED |
| OBOeg Building Materials INC. | Matawan | NJ | — | ◇ UNVERIFIED |
| OFOem Fabricators INC | Neillsville | WI | — | ◇ UNVERIFIED |
| OSOesterlings Sandblasting/butler | Butler | PA | — | ◇ UNVERIFIED |
| OIOfab, INC. | Ocala | FL | — | ◇ UNVERIFIED |
| OAOgden Art Metal INC. | Murray | UT | — | ◇ UNVERIFIED |
| OOgletree's | Saint Helena | CA | — | ◇ UNVERIFIED |
| OCOglivie Company INC the | Astoria | OR | — | ◇ UNVERIFIED |
| OHO H I Company | Stockton | CA | — | ◇ UNVERIFIED |
| OCOhi Company | Stockton | CA | — | ◇ UNVERIFIED |
| OSOhio Steel Industries (0145000318) | Pataskala | OH | — | ◇ UNVERIFIED |
| OSOhio Steel Industries, INC. | Summit Station | OH | — | ◇ UNVERIFIED |
| OVOhio Valley Fabrication and Energy INC. | Wheeling | WV | — | ◇ UNVERIFIED |
| OOhmstede | La Porte | TX | — | ◇ UNVERIFIED |
| OIOiw, INC. | Pelham | AL | — | ◇ UNVERIFIED |
| OLOiw LLC | Oakdale | PA | — | ◇ UNVERIFIED |
| OKO & K American CORP. | Chicago | IL | — | ◇ UNVERIFIED |
| OSOklahoma Stair Craft, INC. | Sapulpa | OK | — | ◇ UNVERIFIED |
| OBOld Bridge Metal Fabrication Inc. | Riverside | CA | — | ◇ UNVERIFIED |
| OIOldcastle Infrastructure - Azusa 10th | Azusa | CA | — | ◇ UNVERIFIED |
| OIOldcastle Infrastructure - Azusa Dalou | Azusa | CA | — | ◇ UNVERIFIED |
| OSOld South Ironworks INC | Gray | TN | — | ◇ UNVERIFIED |
| OWOld World Iron | Gilroy | CA | — | ◇ UNVERIFIED |
| OOOliver's Ornamental Iron, LLC | Flora | MS | — | ◇ UNVERIFIED |
| OCOlson & Company Steel | Fresno | CA | — | ◇ UNVERIFIED |
| OIOlson Iron & Stone Creations LLC | Elk River | MN | — | ◇ UNVERIFIED |
| OSOlson Steel | San Leandro | CA | — | ◇ UNVERIFIED |
| OTOlympus Technologies Incorporated | Eugene | OR | — | ◇ UNVERIFIED |
| ONOmega Natchiq New Iberia Facility | New Iberia | LA | — | ◇ UNVERIFIED |
| OSOmega Steel Products, INC | Jemison | AL | — | ◇ UNVERIFIED |
| OMO & M Fabricators, LLC | Pensacola | FL | — | ◇ UNVERIFIED |
| OIOmni Industrial Services | Buffalo | WV | — | ◇ UNVERIFIED |
| OEOne Ez Post LLC | Kingsport | TN | — | ◇ UNVERIFIED |
| OSOne Source Systems LLC | Vicksburg | MS | — | ◇ UNVERIFIED |
| OFOnGuard Fence Systems, Ltd. | Moorestown | NJ | — | ◇ UNVERIFIED |
| OTOn Time Fab INC | Saint Joseph | KY | — | ◇ UNVERIFIED |
| OFOpc Fabrication and Equipment, INC. (fn) | Phoenix | AZ | — | ◇ UNVERIFIED |
| OSOrange State Steel | Bartow | FL | — | ◇ UNVERIFIED |
| OSOrange State Steel Construction, INC | Pinellas Park | FL | — | ◇ UNVERIFIED |
| OSOrange State Steel Construction, INC. | Riverview | FL | — | ◇ UNVERIFIED |
| OCOrco Construction Supply | Bloomington | CA | — | ◇ UNVERIFIED |
| ODOreco Duct System INC | Baldwin Park | CA | — | ◇ UNVERIFIED |
| OIOregon Iron Works Hidden Way | Vancouver | WA | — | ◇ UNVERIFIED |
| OIOregon Iron Works INC 3001 | Vancouver | WA | — | ◇ UNVERIFIED |
| OPOregon Pacific Structural Fabrication, LLC | Mulino | OR | — | ◇ UNVERIFIED |
| OTOrganic Transit INC. | Durham | NC | — | ◇ UNVERIFIED |
| OEOri Enterprises LLC | Price | UT | — | ◇ UNVERIFIED |
| OMOrion Marine Construction, INC | Tampa | FL | — | ◇ UNVERIFIED |
| OIOrlando Iron Works | Paterson | NJ | — | ◇ UNVERIFIED |
| ODOrnamental Design Inc | Tampa | FL | — | ◇ UNVERIFIED |
| OIOrnamental Iron Concept,bartolome Fluxa | Van Nuys | CA | — | ◇ UNVERIFIED |
| OIOrnamental Ironworks | Los Angeles | CA | — | ◇ UNVERIFIED |
| OMOrnamental Metalworks INC | Decatur | IL | — | ◇ UNVERIFIED |
| OWOsborne Welding, INC. | Hampton | VA | — | ◇ UNVERIFIED |
| ODOscar Diaz Rivera | San Juan | PR | — | ◇ UNVERIFIED |
| OAOshkosh Aerotech - Jetway Systems | Ogden | UT | — | ◇ UNVERIFIED |
| OIOssi's Iron Works | Las Vegas | NV | — | ◇ UNVERIFIED |
| OOOsuna Ornamental LLC | Miami | FL | — | ◇ UNVERIFIED |
| OSOutland Steel, INC. | Caldwell | ID | — | ◇ UNVERIFIED |
| OIOutlaw Industries, LLC | Clinton | LA | — | ◇ UNVERIFIED |
| OSOwens & Sons, INC. | Metairie | LA | — | ◇ UNVERIFIED |
| OBOzark Barge & Dock Service Inc.* | Gravois Mills | MO | — | ◇ UNVERIFIED |
| PIPacal Industries LLC | La Crosse | WI | — | ◇ UNVERIFIED |
| PEPacific Embedment Products | Adelanto | CA | — | ◇ UNVERIFIED |
| PFPacific Fabrication INC | Rancho Cucamonga | CA | — | ◇ UNVERIFIED |
| PMPacific Metal Works INC | Beaverton | OR | — | ◇ UNVERIFIED |
| PRPacific Rebar INC | Ontario | CA | — | ◇ UNVERIFIED |
| PSPacific Steel Group | Benicia | CA | — | ◇ UNVERIFIED |
| PSPacific Steel Group | Napa | CA | — | ◇ UNVERIFIED |
| PSPacific Steel Group | Bloomington | CA | — | ◇ UNVERIFIED |
| PSPacific Steel Group | Bloomington | CA | — | ◇ UNVERIFIED |
| PSPacific Steel Group | Livermore | CA | — | ◇ UNVERIFIED |
| PSPacific Steel Group | Stockton | CA | — | ◇ UNVERIFIED |
| PWPacific Waterjet Cutting INC | Chico | CA | — | ◇ UNVERIFIED |
| PWPacific Welding Services | Asan | GU | — | ◇ UNVERIFIED |
| PTPalmer Tool Company | Camden | TN | — | ◇ UNVERIFIED |
| PSPalmetto Southern INC | Lexington | SC | — | ◇ UNVERIFIED |
