NiSource Inc. is an energy holding company and together with its subsidiaries provides natural gas, electricity and other products and services in the U.S. NiSource has one of the nation's largest natural gas distribution networks as measured by number of customers. NiSource's principal subsidiary is NiSource Gas Distribution Group, Inc., which is a natural gas distribution holding company. The company generates the majority of its operating income from its rate-regulated businesses. Through its wholly-owned subsidiary NiSource Gas Distribution Group, it owns distribution subsidiaries that provide natural gas to residential, commercial and industrial customers.