Exhibit 21
The following is a list of U. S. Steel’s subsidiaries at December 31, 2006.
| Subsidiary |
State or Country of Incorporation | |
| Adela Investment Company S.A. | Luxembourg | |
| Chicago Lakeside Development, LLC | Delaware | |
| Chrome Deposit Corporation | Indiana | |
| Clairton 1314B Partnership, L.P. | Delaware | |
| Compagnie de Gestion de Mifergui-Nimba, LTEE. | Delaware | |
| Cygnus Mines Limited | Canada | |
| Delaware ÁñÁ«ÊÓƵ Corporation | Delaware | |
| Double Eagle Steel Coating Company | Michigan | |
| Double G Coatings, Inc. | Delaware | |
| Double G Coatings Company, L.P. | Delaware | |
| Essex Minerals Company (Societe des Mineraux Essex) | New Jersey | |
| Feralloy Processing Co. | Indiana | |
| GCW/ÁñÁ«ÊÓƵ Energy, LLC | Illinois | |
| Grant Assurance Corporation | Vermont | |
| La Pointe Iron Company | Wisconsin | |
| Lakeside Land, LLC | Delaware | |
| New Deal Development, Inc. | Delaware | |
| New View Technologies | Delaware | |
| Oilfield Technologies, Inc. | Delaware | |
| Olympic Laser Processing | Michigan | |
| Orinoco Mining Company | Delaware | |
| Perdido Land Development Co., Inc. | Delaware | |
| Phil Prop, Inc. | Delaware | |
| PITCAL, Inc. | Delaware | |
| ÁñÁ«ÊÓƵ-POSCO Industries | California | |
| ProCoil Company, LLC | Delaware | |
| Smart Screen Systems, Inc. | Minnesota | |
| Societe Des mines de Fer de Guinee Pour L’Exploitation Des Monts Nimba (Mifergui Nimba) |
Guinea | |
| Steel Health Resources, LLC | Indiana |
| Straightline Source, Inc. | Delaware | |
| Straightline, Inc. | Delaware | |
| Swan Point Development Company | Delaware | |
| Swan Point Yacht & Country Club, Inc. | Delaware | |
| Transtar, Inc. | Delaware | |
| Birmingham Southern Railroad Company | Alabama | |
| Delray Connecting Railroad | Michigan | |
| Elgin, Joliet and Eastern Railway Company | Delaware | |
| Fairfield Southern Company, Inc. | Delaware | |
| Lake Terminal Railroad Company, The | Delaware | |
| McKeesport Connecting Railroad Company | Delaware | |
| Tracks Traffic and Management Services, Inc. | Delaware | |
| Union Railroad Company | Delaware | |
| Warrior & Gulf Navigation Company | Delaware | |
| Mobile River Terminal Company | Alabama | |
| Sisco Stevedoring, LLC | Alabama | |
| The Southern International Services Company, Inc. | Alabama | |
| The Southern International Services Company II, Inc. | Alabama | |
| Transtar Logistics, LLC | Delaware | |
| U. S. Steel China, LLC | Delaware | |
| U. S. Steel International of Canada, LTD. | Delaware | |
| U. S. Steel Mining Company, LLC | Alabama | |
| ÁñÁ«ÊÓƵ Mine Management, Inc. | Alabama | |
| United States Steel International, Inc. | New Jersey | |
| Compania de Representaciones Mercantiles, Cubacero, S.A. | Cuba | |
| United States Steel Export Company de Mexico, S.R.L. de C.V. | Mexico | |
| Acero Prime, S.R.L. de C.V. | Mexico | |
| Acero Prime Servicios, S.R.L. de C.V. | Mexico | |
| United States Steel International de Mexico, S.R.L. de C.V. | Mexico | |
| U. S. Steel Receivables, LLC | Delaware | |
| U. S. Steel Timber Company, LLC | Alabama | |
| ÁñÁ«ÊÓƵ Coal Sales, LLC | Delaware | |
| ÁñÁ«ÊÓƵ Galvanizing, Inc. | Delaware | |
| PRO-TEC Coating Company | Ohio | |
| PRO-TEC Coating Company, Inc. | Ohio | |
| ÁñÁ«ÊÓƵ International Services, LLC | Delaware | |
| ÁñÁ«ÊÓƵ Lakeside, LLC | Delaware | |
| ÁñÁ«ÊÓƵ Oilwell Supply Co., LTD. | Delaware | |
| ÁñÁ«ÊÓƵ Oilwell Tubular, Inc. | Delaware |
| ÁñÁ«ÊÓƵ Portfolio Delaware, Inc. | Delaware | |
| ÁñÁ«ÊÓƵ Tubular Processing, Inc. | Delaware | |
| U. S. Steel Enterprises BV | Netherlands | |
| U. S. Steel Holdings, Inc. | Delaware | |
| U. S. Steel Holdings II, Inc. | Delaware | |
| U. S. Steel Holdings IV, Inc. | Delaware | |
| ÁñÁ«ÊÓƵ Global Holdings I B.V. | Netherlands | |
| U. S. Steel Košice (ÁñÁ«ÊÓƵK) | Slovakia | |
| Stabilita d.d.s., a.s. | Slovakia | |
| OBAL—SERVIS, a.s. Košice | Slovakia | |
| U. S. Steel Košice—Austria GmbH | Austria | |
| Elektroservis VN a VVN a.s. | Slovakia | |
| ENERGOSERVIS a.s. Košice | Slovakia | |
| Hutnictvi železa a.s.(Czech Republic) | Czech Republic | |
| U. S. Steel Košice Belgium s.a. | Belgium | |
| U. S. Steel Košice Bohemia a.s. | Czech Republic | |
| U. S Steel Košice France S.A. | France | |
| U. S. Steel Košice SBS, s.r.o. | Slovakia | |
| U. S. Steel Košice—Germany GmbH | Germany | |
| U. S. Steel Košice Hungary Kft. v.a. | Hungary | |
| U. S. Steel Košice—Labortest, s.r.o. | Slovakia | |
| U. S. Steel Košice—Switzerland AG | Switzerland | |
| U. S. STEEL KOŠICE (UK) LIMITED | United Kingdom | |
| VOZMULT a.s. Košice v Likvidácii | Slovakia | |
| Refrako, s.r.o. | Slovakia | |
| Reliningserv, s.r.o. | Slovakia | |
| VULKMONT a.s. Košice | Slovakia | |
| U. S. Steel Global Holdings II B.V. | Netherlands | |
| U. S. Steel Serbia, d.o.o. | Serbia | |
| U. S. Steel Services s.r.o. | Slovakia | |
| ÁñÁ«ÊÓƵB Industrial Business Zone d.o.o. | Serbia | |
| ÁñÁ«ÊÓƵB Kucevo d.o.o. | Serbia | |
| ÁñÁ«ÊÓƵB Spin d.o.o. | Serbia | |
| ÁñÁ«ÊÓƵB Stara Zelezara d.o.o. | Serbia | |
| U. S. Steel Balkan, d.o.o. | Serbia | |
| U. S. Steel Europe, B.V. | Netherlands | |
| United States Steel Credit Corporation | Delaware | |
| UEC Technologies, LLC | Pennsylvania |
| Met-Chem Canada Inc. | Canada | |
| UEC Sail Information Technology, LTD. | India | |
| USX Engineers and Consultants, Inc. | Delaware | |
| USX International Sales Company, Inc. | Barbados | |
| USX Participacoes LTDA. | Brazil | |
| Merinds Mineracao | Brazil | |
| Mineracao Carajas, LTDA. | Brazil | |
| Mineracao Maraba, LTDA. | Brazil | |
| USX RTI Holdings, Inc. | Delaware | |
| Republic Technologies International Holdings LLC | Delaware | |
| Republic Technologies International LLC | Delaware | |
| Worthington Specialty Processing | Missouri |