Wadsworth was born in Duxbury, Massachusetts, to Peleg and Susanna (Sampson) Wadsworth. He graduated from Harvard College with an A.B. (1769) and an A.M. (1772), and taught school for several years in Plymouth, Massachusetts, with his former classmate Alexander Scammel. There he met Elizabeth Bartlett (1753 to 1825), whom he married in 1772.
==American Revolutionary War==
The Wadsworths lived in Kingston, Massachusetts, until 1775, when Wadsworth recruited a company of minutemen, of which he was chosen captain. His company mustered in response to the alarms generated by the Battle of Lexington and Concord on April 19, 1775. The Plymouth County battalion, commanded by Col. Theophilus Cotton marched to Marshfield, Massachusetts to attack a garrison of British troops there. The attack was delayed for two days, allowing the British time to escape Marshfield by sea. During that time, Capt. Wadsworth, frustrated with the delay, advanced his company to within firing range of the British encampment, nearly instigating combat.
Wadsworth served as aide to Gen. Artemas Ward in March 1776, and as an engineer under Gen. John Thomas in 1776, assisting in laying out the defenses of Roxbury, Massachusetts. He was present at the Battle of Long Island on August 1, 1776. He was made brigadier general of militia in 1777 and Adjutant General of Massachusetts in 1778.
Wadsworth’s finest military engagement was in one of the worst American military defeats of the war. In the summer of 1779 he served as second in command to General Solomon Lovell over the land forces sent to make a combined arms attack on the British fort at Castine, in the so-called Penobscot Expedition. Commodore Dudley Saltonstall was in command of the naval forces. Lt. Colonel Paul Revere also served in this expedition as commander of artillery. While General Lovell remained aboard the Commodore’s vessel, Wadsworth and Revere landed with the infantry and artillery and laid siege to the fort for about two weeks. Due to the reluctance of the Commodore to launch a naval attack in support of the ground forces, the British garrison held out until ships of the Royal Navy arrived from New York and drove the American Navy up the Penobscot River where all 43 American warships were sunk or were scuttled and burned, comprising most of the American fleet, making it the worst American naval disaster prior to the Japanese attack on Pearl Harbor in 1941. Wadsworth, still with the forces on shore organized and led a successful overland retreat through the Maine frontier. Colonel Revere and Commodore Saltonstall were court-martialed for their roles in the debacle (Revere was acquitted, Saltonstall was “dismissed the service”).
In March 1780, Peleg was given command of all the troops raised for the defense of the Province of Maine. On February 17, 1781, British soldiers overran his headquarters in Thomaston. Wadsworth was captured and imprisoned in Fort George at Bagaduce (Castine) (the same fort he had led the attack against in the summer of 1779), but he and fellow prisoner Maj. Benjamin Burton eventually escaped by cutting a hole in the ceiling of their jail and crawling out along the joists. Wadsworth then returned to his family in Plymouth, where he remained until the war’s end.
==After War Years==
In April 1784 Wadsworth returned to Maine, purchased 1.5 acres (6,000 m²) of land on Back Street (now Congress Street in Portland), engaged in surveying, and opened a store in early 1785. There he also built a house, now the historic Wadsworth-Longfellow House. He headed the committee that organized the first convention to discuss independence for Maine from Massachusetts, held in January 1786. He and his wife had ten children, one of whom later gave birth to poet Henry Wadsworth Longfellow. Although he continued to live in Portland, in 1790 he purchased 7800 acres (30 km²) from the Commonwealth in what became the town of Hiram, Maine, settled his son Charles there in 1795, and in 1800 built Wadsworth Hall there for his retirement.
In 1792 Wadsworth was chosen a presidential elector and a member of the Massachusetts Senate, and from 1793-1807 was the first representative in Congress from the region of Massachusetts that later became Maine. In January 1807 he moved to Hiram where he incorporated the township (February 27, 1807) and served as selectman, treasurer and magistrate. For the remainder of his life he devoted himself to farming and local concerns. He died in Hiram on July 18, 1829, and is buried in the family cemetery at Wadsworth Hall.