Northern boundary of Massachusetts

The majority of the boundary is roughly a straight line from the northwest corner of the state (42°44′44.7″N 73°15′54.13″W / 42.745750°N 73.2650361°W / 42.745750; -73.2650361 NAD27[1]) east to a point in Dracut, just north of Lowell.

East of that point, the border is a series of line segments about 3 miles (5 km) north of the curving Merrimack River, ending in the Atlantic Ocean.

The line of latitude three miles south of the river's southernmost bend, approximately 42°2′ north, forms the basis of the southern border of Massachusetts to the present day.

With respect to the southern boundary of New Hampshire, the two provinces disagreed on the meaning of "three miles northward of the Merrimack River, or any part thereof".

From there a line was to be drawn due west to meet the western boundary of Massachusetts (fixed in 1773 with the Province of New York).

A ruling by King George III established the ordinary low-water line on the west bank of the Connecticut River to be the border, but the territory between the Connecticut River and Lake Champlain – which had been sold off by New Hampshire – declared independence in 1777 as the Vermont Republic.