Preston King was born in Ogdensburg, New York on 14th October, 1806. After graduating from Union College in 1827 he studied law and was admitted to bar and commenced practice in St. Lawrence County. He was also appointed as postmaster of Ogdensburg (1831-34).

A member of the Democratic Party he was elected to the 28th Congress and served from March, 1843 to March, 1847. He moved to the Free Soil Party and again served in the 31st and 32nd Congress (March, 1849 to March, 1853). King joined the new Republican Party and was elected to Congress in 1856 but decided not to seek re-election when his term ended in March, 1863.

When Andrew Johnson became president on 15th April, 1865, he invited King to Washington and served as his adviser. Appointed collector of the port of New York, Preston King committed suicide soon afterwards by jumping from a ferryboat in the harbour on 12th November, 1865.