|Langdon was born in 1741 at or near Portsmouth, NH. His father, whose family had emigrated to America before 1660, was a prosperous farmer who sired a large family. The youth's education was intermittent. He attended a local grammar school, worked as an apprentice clerk, and spent some time at sea. Eventually he went into the mercantile business for himself and prospered.|
Langdon, a vigorous supporter of the Revolution, sat on the New Hampshire committee of correspondence and a nonimportation committee. He also attended various patriot assemblies. In 1774 he participated in the seizure and confiscation of British munitions from the Portsmouth fort.
The next year, Langdon served as speaker of the New Hampshire assembly and also sat in the Continental Congress (1775-76). During the latter year, he accepted a colonelcy in the militia of his state and became its agent for British prizes on behalf of the Continental Congress, a post he held throughout the war. In addition, he built privateers for operations against the British--a lucrative occupation.
Langdon also actively took part in the land war. In 1777 he organized and paid for Gen. John Stark's expedition from New Hampshire against British Gen. John Burgoyne and was present in command of a militia unit at Saratoga, NY, when the latter surrendered. Langdon later led a detachment of troops during the Rhode Island campaign, but found his major outlet in politics. He was speaker of the New Hampshire legislature from 1777 to 1781. In 1777, meantime, he had married Elizabeth Sherburne, who was to give birth to one daughter.
In 1783 Langdon was elected to the Continental Congress; the next year, to the state senate; and the following year, as president, or chief executive, of New Hampshire. In 1784 he built a home at Portsmouth. In 1786-87 he was back again as speaker of the legislature and during the latter year for the third time in the Continental Congress.
Langdon was forced to pay his own expenses and those of Nicholas Gilman to the Constitutional Convention because New Hampshire was unable or unwilling to pay them. The pair did not arrive at Philadelphia until late July, by which time much business had already been consummated. Thereafter, Langdon made a significant mark. He spoke more than 20 times during the debates and was a member of the committee that struck a compromise on the issue of slavery. For the most part, his sympathies lay on the side of strengthening the national government. In 1788, once again as state president (1788-89), he took part in the ratifying convention.
From 1789 to 1801 Langdon sat in the U.S. Senate, including service as the first President pro tem for several sessions. During these years, his political affiliations changed. As a supporter of a strong central government, he had been a member of the Federalist Party, but by the time of Jay's Treaty (1794) he was opposing its policies. By 1801 he was firmly backing the Democratic-Republicans.
That year, Langdon declined Jefferson's offer of the Secretaryship of the Navy. Between then and 1812, he kept active in New Hampshire politics. He sat again in the legislature (1801-5), twice holding the position of speaker. After several unsuccessful attempts, in 1805 he was elected as governor and continued in that post until 1811 except for a year's hiatus in 1809. Meanwhile, in 1805, Dartmouth College had awarded him an honorary doctor of laws degree.
In 1812 Langdon refused the Democratic-Republican Vice-Presidential nomination on the grounds of age and health. He enjoyed retirement for another 7 years before he died at the age of 78. His grave is at Old North Cemetery in Portsmouth.