Arkansas: 
Arkansas Oklahoma Gas
Arkansas Western Gas 
CenterPoint Energy

Colorado: 
Xcel Energy (PSCO) 
Atmos Energy 

llinois:
Ameren (CIPS, CILCO, IP) 
Nicor 
North Shore 
Peoples Gas Light & Coke

Indiana:
Citizens 
Fountaintown Gas 
NIPSCO 
Ohio Valley Gas 
Sycamore Gas Company 
Vectren North 
Vectren South 

Iowa:
Alliant 
Black Hills Energy 
MidAmerican Energy

Kansas:
Atmos Energy 
Kansas Gas Service
Black Hills Energy 

Kentucky:
Atmos Energy 
Columbia Gas of Kentucky 
Louisville Gas & Electric 

Louisiana:
CenterPoint Energy 

Michigan:
Consumers Energy 
DTE MichCon 
Michigan Gas Utilities

Minnesota:
CenterPoint Energy 
Minnesota Energy Resources 
Xcel Energy

Mississippi: 
Atmos Energy
CenterPoint Energy

Missouri:
Atmos Energy
Ameren (UE)
LaClede Gas Company

Nebraska:
Black Hills Energy 
Metropolitan Utility District 
Northwestern Energy 
SourceGas 

Ohio:
(direct pipeline connections) 

Oklahoma:
CenterPoint Energy 
Oklahoma Natural Gas 

South Dakota:
Northwestern Energy

Texas:
Atmos Energy 
CenterPoint Energy

West Virginia:
Mountaineer Gas  

Wisconsin
Alliant
Madison Gas & Electric
Wisconsin Public Service
WE Energies

Wyoming:
SourceGas