|                                                                                                              |                                                                           | Exhibit                21                                                                          |
|-------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------|
| **Affiliates                and Subsidiaries of Integrys Energy Group, Inc.****December                31, 2006** |
|                                                                                                              |
|                                                                                                              |                                                                           |                                                                                               |
| INTEGRYS                ENERGY GROUP, INC. + *                                                                    |
|                                                                                                              |
|                                                                                                              | Wedge                Acquisition Corp.++++                                     |
|                                                                                                              |                                                                           |
|                                                                                                              | Wisconsin                Public Service Corporation +                          |
|                                                                                                              |                                                                           | **^**WPS                Leasing,                Inc. +                                             |
|                                                                                                              |                                                                           | Wisconsin                Valley Improvement Company (27.1% ownership) +                            |
|                                                                                                              |                                                                           | Wisconsin                River Power Company (50% ownership) +                                     |
|                                                                                                              |                                                                           | WPS                Investments, LLC (approximately 21.19% ownership) +                             |
|                                                                                                              |                                                                           |                                                                                               | American                Transmission Company LLC (approximately 30.65% ownership)                + |
|                                                                                                              |                                                                           | ATC                Management                Inc. (28.55% ownership) +                             |
|                                                                                                              |                                                                           |
|                                                                                                              | WPS                Investments, LLC (approximately 72.92% ownership) +         |
|                                                                                                              |                                                                           | American                Transmission Company LLC (approximately 30.65% ownership)                + |
|                                                                                                              |                                                                           |
|                                                                                                              | **^**WPS                Nuclear                Corporation +                   |
|                                                                                                              |                                                                           |                                                                                               |
|                                                                                                              | Michigan                Gas                Utilities Corporation ++            |
|                                                                                                              |                                                                           |
|                                                                                                              | Minnesota                Energy Resources Corporation ++                       |
|                                                                                                              |                                                                           |
|                                                                                                              | WPS                Visions,                Inc. +                              |
|                                                                                                              |                                                                           |
|                                                                                                              | Badger                Energy                Services, LLC (12.50% ownership) + |
|                                                                                                              |                                                                           |
|                                                                                                              | WPS                Resources                Capital Corporation +              |
|                                                                                                              |                                                                           | Integrys                Energy Services, Inc. +                                                    |
|                                                                                                              |                                                                           |                                                                                               | Quest                Energy,                LLC +++ |
|                                                                                                              |                                                                           |                                                                                               | Integrys                Energy Services of Canada Corp. (formed under Canadian                law) |
|                                                                                                              |                                                                           |                                                                                               | Integrys                Energy Services of New York, Inc. (formed under New York                law) |
|                                                                                                              |                                                                           |                                                                                               | Integrys                Energy Services of Texas, LP (formed under Texas law) |
|                                                                                                              |                                                                           |                                                                                               | Winnebago                Energy Center, LLC ++ |
|                                                                                                              |                                                                           |                                                                                               | 3096210                Nova                Scotia Company (formed under Canadian law) |
|                                                                                                              |                                                                           |                                                                                               |   | Boralex                WPS                Power Limited Partnership (49.9% ownership) (formed under Canadian                law) |
|                                                                                                              |                                                                           |                                                                                               | WPS                Power                Development, LLC+ |
|                                                                                                              |                                                                           |                                                                                               |   | PDI                Stoneman,                Inc. + |
|                                                                                                              |                                                                           |                                                                                               |   |   | Mid-American                Power, LLC + |
|                                                                                                              |                                                                           |                                                                                               |   | WPS                Canada                Generation, Inc. + |
|                                                                                                              |                                                                           |                                                                                               |   |   | Boralex                WPS                Energy, Inc. (50% ownership) (formed under Canadian                law) |
|                                                                                                              |                                                                           |                                                                                               |   |   |   | Boralex                WPS                Power Limited Partnership (0.2% ownership) (formed under Canadian                law) |
|                                                                                                              |                                                                           |                                                                                               |   | WPS                New                England Generation, Inc. + |
|                                                                                                              |                                                                           |                                                                                               |   | Wisconsin                Woodgas LLC + |
|                                                                                                              |                                                                           |                                                                                               |   | Wisconsin                Energy Operations LLC (49% ownership) + |
|                                                                                                              |                                                                           |                                                                                               |   | ECO                Coal                Pelletization #12 LLC (70% ownership) ++ |
|                                                                                                              |                                                                           |                                                                                               |   |   | Synfuel                Solutions, LLC (33.33% ownership) ++ |
|                                                                                                              |                                                                           |                                                                                               |   |   |   | Synfuel                Solutions Operating, LLC ++ |
|                                                                                                              |                                                                           |                                                                                               |   | Sunbury                Holdings, LLC ++ |
|                                                                                                              |                                                                           |                                                                                               |   |   | WPS                Westwood                Generation, LLC ++ |
|                                                                                                              |                                                                           |                                                                                               |   | WPS                Empire                State, Inc. (formed under New York law) |
|                                                                                                              |                                                                           |                                                                                               |   |   | WPS                Beaver                Falls Generation, LLC ++ |
|                                                                                                              |                                                                           |                                                                                               |   |   | WPS                Niagara                Generation, LLC ++ |
|                                                                                                              |                                                                           |                                                                                               |   |   | WPS                Syracuse                Generation, LLC ++ |
|                                                                                                              |                                                                           |                                                                                               |   | Combined                Locks                Energy Center, LLC** |
|                                                                                                              |                                                                           |                                                                                               |   |

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|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          |
|-------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| **Affiliates                and Subsidiaries of Integrys Energy Group, Inc.****December                31, 2006** |
|                                                                                                              |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          |
| INTEGRYS                ENERGY GROUP, INC. *                                                                      |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          |   |   |
|                                                                                                              | Upper                Peninsula Power Company +++                                                                                                                                                                                                                                                                                                                                                                              |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          | WPS                Investments, LLC (approximately 5.89% ownership) + |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          |   | American                Transmission Company LLC (approximately 30.65% ownership)                + |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          | ATC                Management                Inc. (2.15% ownership) + |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          |   |   |   |
|                                                                                                              | **^**Upper                Peninsula Building Development Company +++                                                                                                                                                                                                                                                                                                                                                          |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          |   |   |   |
|                                                                                                              | Penvest,                Inc.                +++                                                                                                                                                                                                                                                                                                                                                                               |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          | Super                Com                Limited Partnership of Northern Michigan (22.5% ownership)                +++ |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          |
|                                                                                                              | Brown                County                C-LEC, LLC (40% ownership) +                                                                                                                                                                                                                                                                                                                                                       |
|                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                          |
| *                                                                                                                 | Integrys                Energy Group, Inc. is the parent holding company. All affiliated                companies                listed are 100% owned except as noted                otherwise. All affiliates are currently active, with the exception                of                3096210 Nova Scotia Company, Boralex WPS Power Limited Partnership,                and                Boralex WPS Energy, Inc. |
| **                                                                                                                | An                exempt                wholesale generator.                                                                                                                                                                                                                                                                                                                                                                  |
| +                                                                                                                 | Formed                under                Wisconsin Law                                                                                                                                                                                                                                                                                                                                                                      |
| ++                                                                                                                | Formed                under                Delaware Law                                                                                                                                                                                                                                                                                                                                                                       |
| +++                                                                                                               | Formed                under                Michigan Law                                                                                                                                                                                                                                                                                                                                                                       |
| **++++**                                                                                                          | Formed                under                Illinois Law                                                                                                                                                                                                                                                                                                                                                                       |
| ^                                                                                                                 | Provides                non-power goods or services to a public utility or natural gas                company.                                                                                                                                                                                                                                                                                                                |

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