William P. Fessenden (1864–1865)
William Pitt Fessenden was born in 1806 in Merrimack County, New Hampshire. He graduated from Bowdoin College in 1823, studied law, was admitted to the state bar in 1827, and began practicing in Maine.
After serving in the state legislature as a Whig in 1832, Fessenden practiced law until his return to the state legislature in 1840. He was elected to the U.S. House of Representatives and served from 1841 to 1843. Fessenden decided not to run for reelection and returned home to Maine, where he served in the state legislature from 1845 to 1846.
In 1853, Fessenden was elected to the United States Senate as a Whig and remained until 1864 when he resigned -- as a Republican -- to become Abraham Lincoln’s secretary of the treasury. Fessenden’s tenure in the cabinet lasted until 1865; he left to resume his duties as a United States Senator from Maine. It was in this capacity that he voted against the impeachment of Andrew Johnson -- one of only seven Republican senators to do so. Although his party shunned him as a result, William Pitt Fessenden served in the Senate until his death in 1869.