Langdon became an active
Federalist. He practiced law in
Windsor, but later returned to Castleton. He served as the
Rutland County Register of Probate from 1792 to 1794, in 1796, and again in 1813. He was
Judge of Probate in 1798 and 1799. In 1808 he served on the state Executive Council. He received an honorary degree at
Middlebury Collegein
Vermont in 1803 and was a trustee from 1811 until his death. He was a member of the
Vermont House of Representatives in 1813, 1814, 1817, 1819, 1820, and 1822. Langdon was elected as a
Federalist to the
Fourteenth Congress, serving from March 4, 1815, until March 3, 1817. He was not a candidate for renomination to the
Fifteenth Congress. He was again elected to the Executive Council and served from 1823 until his death. ==Family life==