The Boston Neck was a narrow strip of land leading into Boston.
In the 18th century, the Neck was the only land route into Boston. During the American Revolutionary War, fortifications were built across the Neck to protect the city from a land attack. When the Siege of Boston began in 1775, Governor Gage ordered that the fortifications be expanded and strengthened, to which they eventually became known as "Gage's Lines."
From the 19th century, land was added to Boston Neck, widening it and allowing the city to grow, which also eased traffic on and off the island.