Somerville Massachusetts is an industrial city located northwest of Boston and adjacent to the city of Cambridge. A population of well over 70,000 living within an area comprising slightly over 4 square miles makes Somerville the most densely populated city in New England. Once part of neighboring Charlestown, Somerville became incorporated as a separate town in 1842 and in 1872 the town was incorporated as a city. The ensuing years saw the city's population grow by leaps and bounds, aided by the establishment of streetcar lines and a burgeoning prominence of heavy industry which took root in the city. Like its neighbor Cambridge, Somerville is defined by its city squares, which mark the neighborhood boundaries and also house unique centers of business and entertainment. Among these are Davis Square, Ball Square, Union Square, Teele Square, and Magoun Square.