Columbia Gas of Massachusetts, the assumed name of Bay State Gas Company, was a supplier of retail natural gas to over 300,000 customers in parts of Massachusetts surrounding Springfield, Brockton, and Lawrence. It was a subsidiary of NiSource. The company's operations in New Hampshire and Maine were sold to Unitil Corporation in 2008.
The company received attention after the Merrimack Valley gas explosions in September 2018. In February 2020, it was announced that energy company Eversource would acquire the Massachusetts gas assets of Columbia Gas for $1.1 billion.[1] Columbia Gas was also ordered to pay a $53 million fine for violating the Pipeline Safety Act.[2] The acquisition by Eversource was completed in October 2020, effectively ending Columbia Gas operations in Massachusetts.[3]