Columbia Gas of Kentucky delivers clean, affordable and efficient natural gas to approximately 135,000 customers across the s ... tate. Headquartered in Lexington, it is 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 through its local Columbia Gas and NIPSCO brands. read more