Montana-Dakota Utilities Co., a division of MDU Resource Group Inc. specializes in providing retail natural gas and/or electric service. The firm caters to the needs of its customers throughout Montana, North Dakota, South Dakota and Wyoming. Its service area covers more than 168,000 square miles and over 355,000 customers. MDU Resources Group Inc., a Fortune 500 company, specializes in providing natural resource products and related services. It is a member of the S&P (Standard & Poor's) MidCap 400 index.