Exhibit 21

SEMGROUP CORPORATION

Subsidiaries



|                                    |  |                                    
|----------------------------------- |  | -----------------------------------
|Entity                              |  | Place of
Incorporation/Organization
|                                    | 
|SemGroup Holdings G.P., L.L.C.      |  | Delaware                           
|                                    | 
|SemGroup Holdings, L.P.             |  | Delaware                           
|                                    | 
|SemOperating G.P., L.L.C.           |  | Oklahoma                           
|                                    | 
|SemCap, L.L.C.                      |  | Oklahoma                           
|                                    | 
|SemGroup Asia, L.L.C.               |  | Delaware                           
|                                    | 
|SemManagement, L.L.C.               |  | Delaware                           
|                                    | 
|SemGroup Subsidiary Holding, L.L.C. |  | Delaware                           
|                                    | 
|Rose Rock Midstream Holdings, LLC   |  | Delaware                           
|                                    | 
|Rose Rock Midstream Corporation     |  | Delaware                           
|                                    | 
|Rose Rock Midstream GP, LLC         |  | Delaware                           
|                                    | 
|Rose Rock Midstream, L.P.           |  | Delaware                           
|                                    | 
|Rose Rock Midstream Operating, LLC  |  | Delaware                           
|                                    | 
|Rose Rock Midstream Energy GP, LLC  |  | Delaware                           
|                                    | 
|SemCrude, L.P.                      |  | Delaware                           
|                                    | 
|SemCrude Pipeline, L.L.C.           |  | Delaware                           
|                                    | 
|Rocky Cliffs Pipeline, L.L.C.       |  | Delaware                           
|                                    | 
|Eaglwing, L.P.                      |  | Oklahoma                           
|                                    | 
|SemDevelopment, L.L.C.              |  | Delaware                           
|                                    | 
|SemStream, L.P.                     |  | Delaware                           
|                                    | 
|SemStream Arizona Propane, L.L.C.   |  | Delaware                           
|                                    | 
|SemFuel, L.P.                       |  | Texas                              
|                                    | 
|SemFuel Transport, LLC              |  | Wisconsin                          
|                                    | 
|SemProducts, L.L.C.                 |  | Oklahoma                           
|                                    | 
|SemGas, L.P.                        |  | Oklahoma                           
|                                    | 
|SemKan, L.L.C.                      |  | Oklahoma                           



---

|                                          |  |               
|----------------------------------------- |  | --------------
|                                          | 
|SemGas Gathering, L.L.C.                  |  | Oklahoma      
|                                          | 
|SemGas Storage, L.L.C.                    |  | Oklahoma      
|                                          | 
|Greyhawk Gas Storage Company, L.L.C.      |  | Delaware      
|                                          | 
|Steuben Development Company, LLC          |  | Delaware      
|                                          | 
|Grayson Pipeline, L.L.C.                  |  | Oklahoma      
|                                          | 
|SemCanada, L.P.                           |  | Oklahoma      
|                                          | 
|SemCanada Crude Company                   |  | Nova Scotia   
|                                          | 
|SemCanada II, L.P.                        |  | Oklahoma      
|                                          | 
|SemCAMS ULC                               |  | Nova Scotia   
|                                          | 
|SemCAMS Redwillow ULC                     |  | Nova Scotia   
|                                          | 
|SemGreen, L.P.                            |  | Delaware      
|                                          | 
|SemBio, L.L.C.                            |  | Delaware      
|                                          | 
|SemMaterials, L.P.                        |  | Oklahoma      
|                                          | 
|New Century Transportation LLC            |  | Delaware      
|                                          | 
|K.C. Asphalt, L.L.C.                      |  | Colorado      
|                                          | 
|SemTrucking, L.P.                         |  | Oklahoma      
|                                          | 
|SemMaterials Vietnam, L.L.C.              |  | Oklahoma      
|                                          | 
|Chemical Petroleum Exchange, Incorporated |  | Illinois      
|                                          | 
|SemMexico, L.L.C.                         |  | Oklahoma      
|                                          | 
|SemMexico Materials HC S. de R.L. de C.V. |  | Mexico        
|                                          | 
|SemMaterials HC Mexico S. de R.L. de C.V. |  | Mexico        
|                                          | 
|SemMaterials Mexico S. de R.L. de C.V.    |  | Mexico        
|                                          | 
|SemMaterials SC Mexico S. de R.L. de C.V. |  | Mexico        
|                                          | 
|SemGroup Europe Holding L.L.C.            |  | Delaware      
|                                          | 
|SemEuro Limited                           |  | United Kingdom
|                                          | 
|SemLogistics Milford Haven Limited        |  | United Kingdom
|                                          | 
|SemEuro Supply Limited                    |  | United Kingdom