Eversource Energy is a publicly traded, Fortune 500 energy company headquartered in Hartford, Connecticut, and Boston, Massachusetts, with several regulated subsidiaries offering retail electricity, natural gas service and water service to approximately 4 million customers in Connecticut, Massachusetts, and New Hampshire. Following its 2012 merger with Boston-based NSTAR, Northeast Utilities had more than 4,270 circuit miles of electric transmission lines, 72,000 pole miles of distribution lines, and 6,459 miles of natural gas pipeline in New England. On February 2, 2015, the company and all its subsidiaries rebranded themselves as "Eversource Energy". The stock symbol changed on February 19, 2015, from "NU" to "ES". Corporate structure Before its rebranding, the company operated six main subsidiaries: Connecticut Light and Power (CL&P), Public Service Company of New Hampshire (PSNH), Western Massachusetts Electric Company (WMECO), Yankee Gas Services Company (Yankee Gas), NSTAR Electric, and NSTAR Gas. NSTAR itself was the product of corporate mergers, and included the former Boston Edison Company, Cambridge Electric Light Company, Commonwealth Electric Company, Commonwealth Gas, and Cambridge Gas Company. All now currently operate under the Eversource name. Eversource remains Connecticut's largest electric utility, serving more than 1.2 million residential, municipal, commercial and industrial customers in approximately 149 cities and towns. It also serves approximately 229,000 natural gas customers in 73 cities and towns. Eversource is also New Hampshire's largest electric utility, serving more than 500,000 homes and businesses in 211 cities and towns throughout the state. It is also a main distributor of energy to 1.7 million customers throughout Massachusetts, including more than 1.4 million electric customers in 140 communities and more than 300,000 natural gas customers in 51 communities. History The Rocky River Power Company, formed in 1905 by J. Henry Roraback, became the Connecticut Light and Power Company in 1917. Eversource predecessor Northeast Utilities (NU) was formed on July 1, 1966, with the merger of the Connecticut Light and Power Company (CL&P, formed in 1917), Western Massachusetts Electric Company (WMECO, formed in 1886), and the Hartford Electric Light Company (HELCO, formed in 1878) under a single parent company, creating the first new multi-state public utility holding company since the enactment of the Public Utility Holding Company Act of 1935. In 1967, Holyoke Water Power Company (HWP) (formed in 1859) joined the NU System, and in 1992 the Public Service Company of New Hampshire (PSNH, formed in 1926) followed. After some up-and-down growth under CEO Lelan Sillin (1970–1983)