Jonathan Eddy was born in Norton, Massachusetts in 1726 or 1727. In 1755, he enlisted in the Massachusetts militia and participated in Robert Monckton's successful capture of Fort Beauséjour on the Isthmus of Chignecto in the French and Indian War. He received a militia captain's commission in 1758, when he apparently saw no action, and again in 1759, when his company was garrisoned at Fort Cumberland (the name Fort Beauséjour was given after its capture). After the war, Eddy returned home to Norton, only to return to Cumberland as a New England Planter in 1763. From 1770 to 1775 he served in the Nova Scotia House of Assembly, representing Cumberland Township.