The town was first granted in 1736 by Colonial Governor Jonathan Belcher of Massachusetts as Number 3, third in a line of Connecticut River fort towns. It would be settled as early as 1736, and called Great Falls or Lunenburg. Colonel Benjamin Bellows, for whom Bellows Falls, Vermont is named, built a large fort here for defense against Indian attack. After New Hampshire became a separate province, the town was regranted by Governor Benning Wentworth as Bellowstown, after its founder. It would be incorporated in 1756. The grant was renewed in 1761, when the town was renamed Walpole, in honor of Sir Robert Walpole, 1st Earl of Orford, and first Prime Minister of Great Britain. The first bridge across the Connecticut River, an engineering feat in its day, was built at Walpole in 1785, and is regarded as one of the most famous early spans in the United States. The town contains many architecturally significant old houses, including several associated with Colonel Bellows and members of his family. Walpole Academy, built in 1831 and attributed to master-builder Aaron Prentiss Howland, is listed on the National Register of Historic Places. The abundant lilacs in the town inspired Louisa May Alcott to write the 1878 book Under the Lilacs.