Exhibit 21

Subsidiaries of ONEOK Partners, L.P.



|                                                         |  |                                     
|-------------------------------------------------------- |  | ------------------------------------
|Subsidiary                                               |  | State ofIncorporationor Organization
|Bear Paw Energy, LLC                                     |  | Delaware                            
|Bear Paw Investments, LLC                                |  | Delaware                            
|Bear Paw Processing (Canada) Ltd.                        |  | Alberta                             
|Black Mesa Holdings, Inc.                                |  | Delaware                            
|Black Mesa Pipeline, Inc.                                |  | Delaware                            
|Black Mesa Pipeline Operations, L.L.C.                   |  | Delaware                            
|Black Mesa Pipeline Technologies, Inc.                   |  | Oklahoma                            
|Black Mesa Pipeline Technologies Services, L.L.C. (50%)1 |  | Oklahoma                            
|Brown Bear Enterprises, LLC                              |  | Delaware                            
|Border Midstream Services, Ltd.                          |  | Alberta                             
|Border Midwestern Company                                |  | Delaware                            
|Border Minnesota Pipeline, LLC                           |  | Delaware                            
|Border Viking Company                                    |  | Delaware                            
|Crestone Bighorn, L.L.C.                                 |  | Delaware                            
|Crestone Energy Ventures, L.L.C.2                        |  | Delaware                            
|Crestone Gathering Services, L.L.C.2                     |  | Delaware                            
|Crestone Powder River, L.L.C.3                           |  | Delaware                            
|Crestone Wind River, L.L.C.4                             |  | Delaware                            
|Chisholm Pipeline Company (50%)                          |  | Delaware                            
|Chisholm Pipeline Holdings, L.L.C.                       |  | Delaware                            
|Guardian Pipeline, L.L.C.                                |  | Delaware                            
|Mid Continent Market Center, L.L.C.                      |  | Kansas                              
|Midwestern Gas Marketing Company                         |  | Delaware                            
|Midwestern Gas Transmission Company                      |  | Delaware                            
|Northern Border Pipeline Company                         |  | Texas                               
|OkTex Pipeline Company, L.L.C.                           |  | Delaware                            
|ONEOK Field Services Company, L.L.C.                     |  | Oklahoma                            
|ONEOK Gas Gathering, L.L.C.5                             |  | Oklahoma                            
|ONEOK Gas Storage Holdings, L.L.C.                       |  | Delaware                            
|ONEOK Gas Storage, L.L.C.                                |  | Oklahoma                            
|ONEOK Gas Transportation, L.L.C.                         |  | Oklahoma                            
|ONEOK ILP GP, L.L.C.                                     |  | Delaware                            
|ONEOK Hydrocarbon, L.L.C.                                |  | Delaware                            
|ONEOK Hydrocarbon, L.P.                                  |  | Delaware                            
|ONEOK Hydrocarbon GP, L.L.C.                             |  | Delaware                            
|ONEOK Hydrocarbon Holdings, L.L.C.                       |  | Delaware                            
|ONEOK Hydrocarbon Southwest, L.L.C.                      |  | Delaware                            

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|1 | Black Mesa Pipeline Technologies Services, L.L.C. owns 0.81% of China Pipeline Holdings, Ltd
|- | --------------------------------------------------------------------------------------------

|2 | Crestone Energy Ventures, L.L.C. owns 39% and Crestone Gathering Services, L.L.C. owns 10% of Bighorn Gas Gathering, L.L.C.
|- | ---------------------------------------------------------------------------------------------------------------------------

|3 | Crestone Powder River, L.L.C. owns 37.04% of Fort Union Gas Gathering, L.L.C.
|- | -----------------------------------------------------------------------------

|4 | Crestone Wind River, L.L.C. owns 35% of Lost Creek Gathering Company, L.L.C.
|- | ----------------------------------------------------------------------------

|5 | ONEOK Gas Gathering, L.L.C. owns 48.445% of Sycamore Gas System
|- | ---------------------------------------------------------------



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|                                                        |  |                                     
|------------------------------------------------------- |  | ------------------------------------
|Subsidiary                                              |  | State ofIncorporationor Organization
|ONEOK MB I, L.P.6                                       |  | Delaware                            
|ONEOK Midstream Gas Supply, L.L.C.                      |  | Oklahoma                            
|ONEOK NGL Pipeline, L.P.                                |  | Delaware                            
|ONEOK Overland Pass Holdings, L.L.C.                    |  | Oklahoma                            
|ONEOK Partners Intermediate Limited Partnership         |  | Delaware                            
|ONEOK Sayre Storage Company, L.L.C.                     |  | Delaware                            
|ONEOK Texas Gas Storage, L.P.                           |  | Texas                               
|ONEOK Transmission Company, L.L.C.                      |  | Delaware                            
|ONEOK Underground Storage Company, L.L.C.               |  | Kansas                              
|ONEOK VESCO Holdings, L.L.C.7                           |  | Delaware                            
|ONEOK WesTex Transmission, L.P.                         |  | Delaware                            
|Overland Pass Pipeline Company LLC                      |  | Delaware                            
|Potato Hills Gas Gathering System (joint venture) (51%) |  | Oklahoma                            
|Viking Gas Transmission Company                         |  | Delaware                            

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|6 | ONEOK MB I, L.P. owns 80% of Mont Belvieu I Fractionation Facility
|- | ------------------------------------------------------------------

|7 | ONEOK VESCO Holdings, L.L.C. owns 10.1765% of Venice Energy Services Company, L.L.C.
|- | ------------------------------------------------------------------------------------