Exhibit 21
Affiliates and Subsidiaries of Integrys Energy Group, Inc. December 31, 2009
INTEGRYS ENERGY GROUP, INC.+ *
	Wisconsin Public Service Corporation+
		WPS Leasing, Inc.+
		Wisconsin Valley Improvement Company (27.1% ownership) +
		Wisconsin River Power Company (50% ownership)+
		WPS Investments, LLC (approximately 12.77% ownership)+
			American Transmission Company LLC (approximately 34.07% ownership)+
		ATC Management Inc. (32.11% ownership of Class A Shares, 20% ownership of Class B Shares)+
	WPS Investments, LLC (approximately 84.51% ownership)+
		American Transmission Company LLC (approximately 34.07% ownership)+
	Michigan Gas Utilities Corporation++
	Minnesota Energy Resources Corporation++
	Integrys Business Support, LLC++
	WPS Visions, Inc.+
	Badger Energy Services, LLC (12.50% ownership)+
	Integrys Energy Services, Inc.+
		Integrys Energy Services – Natural Gas, LLC++
		Integrys Energy Services – Electric, LLC++
		Quest Energy, LLC+++
		Integrys Energy Services of Canada Corp. (formed under Canadian law)
		Integrys Energy Services of New York, Inc.++++++
			Integrys Energy Services of Texas, LP+++++ (99% ownership)
		Integrys Energy Services of Texas, LP+++++ (1% ownership)
		PERC Holdings, LLC++
		WPS Power Development, LLC+
			PDI Stoneman, Inc.+
			Winnebago Energy Center, LLC++
			WPS Canada Generation, Inc.+
			WPS New England Generation, Inc.+
			Wisconsin Woodgas LLC+
			Wisconsin Energy Operations LLC (49% ownership)+
			ECO Coal Pelletization #12 LLC++
			Sunbury Holdings, LLC++
				WPS Westwood Generation, LLC++
			WPS Empire State, Inc.++++++
				WPS Beaver Falls Generation, LLC++
				WPS Syracuse Generation, LLC++
			Combined Locks Energy Center, LLC+
			Peoples Natural Gas Liquids, LLC++
			Solar Hold 2008-1, LLC++
				Soltage-MAZ 700 Tinton Falls, LLC++ (99% ownership)
				Soltage-ADC 630 Jamesburg, LLC++  (99% ownership)
				Soltage-PLG 500 Millford, LLC++  (99% ownership)
			Solar Hold 2008-2, LLC++
				Solar Man, LLC++
				Sun Devil Solar LLC++
				Solar Star California II, LLC++
				Solar Star New Jersey, I, LLC++
				Crimson Solar, LLC++
				Solar Star New Jersey, II, LLC++
				Solar Star TM2, LLC++
			LGS Renewables, I, LC+++++ (50% ownership)

Affiliates and Subsidiaries of Integrys Energy Group, Inc. December 31, 2009
INTEGRYS ENERGY GROUP, INC.+*
	Peoples Energy Corporation++++
		The Peoples Gas Light and Coke Company++++
			Peoples Gas Neighborhood Development Corporation++++
		North Shore Gas Company++++
		Peoples Energy Resources Company, LLC++
		Peoples District Energy Corporation++++
		Peoples Energy Ventures, LLC++
			Peoples Energy Home Services, LLC++
			Peoples Energy Neighborhood Development, LLC++
			Peoples Technology, LLC++
	Upper Peninsula Power Company+++
		WPS Investments, LLC (approximately 2.72 ownership)+
				American Transmission Company LLC (approximately 34.07% ownership)+
		ATC Management Inc. (1.96% ownership)+
	Penvest, Inc.+++
*	Integrys Energy Group, Inc. is the parent holding company.  All affiliated companies listed are 100% owned except asnoted otherwise.  All affiliates are currently active, with the exception of Wisconsin Woodgas, LLC;  Wisconsin Energy Operations LLC; ECO Coal Pelletization #12, LLC;PDI Stoneman, Inc.; Peoples Energy Ventures, LLC; and Peoples District Energy Corporation.
+	Formed under Wisconsin law.
++	Formed under Delaware law.
+++	Formed under Michigan law.
++++	Formed under Illinois law.
+++++	Formed under Texas law.
++++++	Formed under New York law.