Prior to British colonization, the Connecticut River valley was populated by bands of the Western Abenaki, who lived in sometimes-large villages of longhouses.

[4] Depending on the season, they would either remain near their villages to fish, gather plants, engage in sugaring, and trade or fight with their neighbors, or head to nearby fowling and hunting grounds.

Within that province, the area that is now Unity was part of a territory chartered in 1753 and named "Buckingham" after John Hobart, 1st Earl of Buckinghamshire.

[1] Grants in the area were given by both the early Massachusetts government and by Governor Benning Wentworth, which led to disputes.

The western and central part of town is drained by the Little Sugar River, leading to the Connecticut at North Charlestown, while the northwestern corner and eastern end of the town are drained by tributaries of the Sugar River, which flows to the Connecticut in Claremont.

The highest point in Unity is an unnamed summit along the town's northern boundary, with an elevation of 2,011 feet (613 m) above sea level.

66.5% were married couples living together, 4.2% had a female householder with no husband present, and 23.6% were non-families.