**Exhibit      21       **

| **SUBSIDIARIES                OF PEOPLES ENERGY CORPORATION**                                                                                                                                                                                                              |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| The                following is a list of subsidiaries of the Company as of September                30,                2006, omitting some subsidiaries which, considered in the aggregate,                would                not constitute a significant subsidiary.  |
|   **Subsidiary**                                                                                                                                                                                                                                                      |  **State                of Incorporation****or                Formation** |
|  The                Peoples Gas Light and Coke Company                                                                                                                                                                                                                     |  Illinois |
| North                Shore Gas Company                                                                                                                                                                                                                                          | Illinois |
| Peoples                Energy Production Company                                                                                                                                                                                                                                | Delaware |
| PEP                Holdings, LLC                                                                                                                                                                                                                                                | Delaware |
| Peoples                Energy Production Operating Company                                                                                                                                                                                                                      | Delaware |
| Peoples                Energy Production Partners, L.P.                                                                                                                                                                                                                         | Delaware |
| Peoples                Energy Production - Texas, L.P.                                                                                                                                                                                                                          | Delaware |
| Peoples                Energy Resources Company, LLC                                                                                                                                                                                                                            | Delaware |
| PERC                Power, LLC                                                                                                                                                                                                                                                  | Delaware |
| Peoples                Elwood, LLC                                                                                                                                                                                                                                              | Delaware |
| Peoples                Calumet, LLC                                                                                                                                                                                                                                             | Delaware |
| PERC                Wholesale Marketing, LLC                                                                                                                                                                                                                                    | Delaware |
| Peoples                Energy Services Corporation                                                                                                                                                                                                                              | Illinois |
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