Northeast Gas Association. Established on January 1, 2003, NGA is a regional trade association, representing the Northeast U.S., that focuses on education and training, technology research and development, operations, planning, and increasing public awareness of natural gas. NGA represents natural gas distribution companies, transmission companies, liquefied natural gas importers and associate member companies in eight states (CT, ME, MA, NH, NJ, NY, RI and VT).