Coos, New Hampshire refers to the frontier

Frontier

A frontier is a political and geographical term referring to areas near or beyond a boundary. 'Frontier' was absorbed into English from French in the 15th century, with the meaning "borderland"--the region of a country that fronts on another country .The use of "frontier" to mean "a region at the...

 area of northern New Hampshire

New Hampshire

New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...

. During the American Revolution

American Revolution

The American Revolution was the political upheaval during the last half of the 18th century in which thirteen colonies in North America joined together to break free from the British Empire, combining to become the United States of America...

 a military command was located at Haverhill, New Hampshire

Haverhill, New Hampshire

Haverhill is a town in Grafton County, New Hampshire, United States. The population was 4,697 at the 2010 census. Haverhill includes the villages of Woodsville, Pike, and North Haverhill, the historic town center at Haverhill Corner, and the district of Mountain Lakes...

 to protect the New Hampshire Grants

New Hampshire Grants

The New Hampshire Grants or Benning Wentworth Grants were land grants made between 1749 and 1764 by the provincial governor of New Hampshire, Benning Wentworth. The land grants, totaling about 135 , were made on land claimed by New Hampshire west of the Connecticut River, territory that was also...

 and to support military efforts in the invasion of Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

.

The name was later given to a portion of northern Grafton County

Grafton County, New Hampshire

Grafton County is a county located in the U.S. state of New Hampshire. As of the 2010 census, the population was 89,118. Its county seat is North Haverhill, which is a village within the town of Haverhill. Until 1972, the county courthouse and other offices were located in downtown Woodsville, a...

 in 1803 when a new county, named Coos

Coos County, New Hampshire

-National protected areas:*Umbagog National Wildlife Refuge *Silvio O. Conte National Fish and Wildlife Refuge *White Mountain National Forest -Demographics:...

, was created.

The location was originally a name associated with a part of the migratory Abenaki tribe. The location was known before 1704 to have military significance for several provincial governments and the leaders in New France

New France

New France was the area colonized by France in North America during a period beginning with the exploration of the Saint Lawrence River by Jacques Cartier in 1534 and ending with the cession of New France to Spain and Great Britain in 1763...

.

In 1755, a Fort Wentworth

Fort Wentworth

Fort Wentworth was built by order of Benning Wentworth in 1755. The fort was built at the junction of the Upper Ammonoosuc River and Connecticut River, in Northumberland, New Hampshire, by soldiers of Colonel Joseph Blanchard's New Hampshire Provincial Regiment including Robert Rogers. In 1759,...

 was to be constructed by Rogers' Rangers

Rogers' Rangers

Rogers' Rangers was an independent company of colonial militia, attached to the British Army during the Seven Years War . The unit was informally trained by Major Robert Rogers as a rapidly deployable light infantry force tasked with reconnaissance and conducting special operations against distant...

 at the junction of the Upper Ammonoosuc River

Upper Ammonoosuc River

The Upper Ammonoosuc River is a tributary of the Connecticut River that flows through Coös County in northern part of the northeastern U.S. state of New Hampshire...

 with the Connecticut River

Connecticut River

The Connecticut River is the largest and longest river in New England, and also an American Heritage River. It flows roughly south, starting from the Fourth Connecticut Lake in New Hampshire. After flowing through the remaining Connecticut Lakes and Lake Francis, it defines the border between the...

 in present-day Northumberland, New Hampshire

Northumberland, New Hampshire

Northumberland is a town located in southwestern Coos County, New Hampshire, U.S., north of Lancaster. It is part of the Berlin, NH–VT micropolitan statistical area...

. A river with a similar name, the Ammonoosuc River

Ammonoosuc River

The Ammonoosuc River is a river, 55 mi long, in northwestern New Hampshire in the United States. It is a tributary of the Connecticut River, which flows to Long Island Sound. "Ammonoosuc" is Abnaki for "small, narrow fishing place"....

, flows through Grafton County, joining the Connecticut opposite Newbury, Vermont

Newbury, Vermont

Newbury could be either of the following places in the U.S. state of Vermont:*Newbury , Vermont*Newbury , Vermont...

. The upper Coos refers to the area around Lancaster, New Hampshire

Lancaster, New Hampshire

Lancaster is a town in Coos County, New Hampshire, USA, on the Connecticut River named after Lancaster, England. As of the 2010 census, the town population was 3,507, the second largest in the county after Berlin. It is the county seat of Coos County and gateway to the Great North Woods Region...

, the county seat of Coos County, and the lower Coos to Newbury, Vermont. The distance between these locations is approximately 40 miles (64.4 km).