From Boston Globe writer Hope Shannon: "For those of you who might not be familiar with Boston's South End neighborhood, until the early 19th century it was a sort of no-man’s land between the main part of Boston on the Shawmut Peninsula and the town of Roxbury on the mainland. The Shawmut Peninsula ('original' Boston) was connected to the mainland and Roxbury by a long isthmus, the Neck, along which ran a main road, today’s Washington Street. "In 1801, the town selectmen, including Charles Bulfinch, presented a plan to develop some of the necklands between the main part of Boston and Roxbury. The newly laid out area was meant to attract freestanding construction and houses surrounded by gardens and grounds. However, few people purchased these lots and by the late 1820s, the city of Boston reevaluated the development of the Neck. They planned more streets and divided the blocks into smaller parcels, hoping to attract a wider demographic with smaller and less expensive lot prices.
"By the 1840s, as foreign immigration to Boston increased, the population of the city grew dramatically and tenement housing began to dominate parts of the city. Boston worried that its middle and upper-middle class tax base would leave for the suburbs. In the late 1840s, the selectmen decided to turn the necklands into a rowhouse district to entice these families to stay within the city limits.
"After the city decided to pursue a rowhouse plan, they laid out three residential style squares in 1850-1851: Chester Square (on Massachusetts Avenue today between Tremont St. and Shawmut Ave.), Worcester Square, and Union Park. These squares feature rowhouses facing a central green space with a fountain. Most of the buildings on these squares were built in the 1850s.
"In general, upper-middle class families, many involved in commercial enterprise, lived in most of the houses on the squares. Other South End streets were also developed into rowhouse streets, housing upper-middle and middle class families. Working class families also lived in the district. Their homes were usually on narrower streets located closer to downtown." Full article here.