Dorchester is a neighborhood comprising more than 6 square miles in the City of Boston, Massachusetts, United States. Originally, Dorchester was a separate town, founded by Puritans who emigrated in 1630 from Dorchester, Dorset, England, to the Massachusetts Bay Colony. This dissolved municipality, Boston's largest neighborhood by far, is often divided by city planners in order to create two planning areas roughly equivalent in size and population to other Boston neighborhoods.