Columbia Gas of Ohio delivers clean, affordable and efficient natural gas to approximately 1.4 million customers across the s ... tate. With headquarters in Columbus, Ohio, it is the largest natural gas utility in Ohio and one of NiSource’s seven regulated utility companies. NiSource (NYSE: NI) 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 seven states through its local Columbia Gas and NIPSCO brands. read more