NiSource Inc. is one of the largest fully regulated utility companies in the United States, serving approximately 3.5 million natural gas customers and 500,000 electric customers across six states through its local Columbia Gas and NIPSCO brands.

NiSource's natural gas utilities provide domestically produced supplies of natural gas to residential, commercial and industrial customers via nearly 60,000 miles of pipeline and related facilities in six states: Indiana, Kentucky, Maryland, Ohio, Pennsylvania and Virginia.

[4] In 2015, NiSource was named to the Dow Jones Sustainability—North America Index for the second year in a row and for the ninth time since 1999.

"[7][8] In December 2011, the progressive activist group Public Campaign criticized NiSource for spending $1.83 million on lobbying and not paying any taxes during 2008–2010, instead getting $227 million in tax rebates, despite making a profit of $1.4 billion across those three years.

NiSource responded by stating: "This law, enacted by Congress, encouraged companies like NiSource to accelerate capital investments to spur economic recovery by permitting portions of these investments to be deducted at an accelerated rate.

At least 25 people were injured, and one was killed; residents from parts of three towns had to be evacuated for a few days and electricity service turned off until the area was inspected for gas.