Hannibal Hamlin served for nearly 50 years as a U.S. representative and senator from Maine, and as 15th vice president of the United States. Hamlin began his political career in the state legislature where he served three terms as Speaker. In 1843 he moved to the U.S. House of Representatives. During his two terms in the House of Representatives, Hamlin played an important role in the debate over slavery. In 1846 he joined forces with other antislavery members to propose an amendment that would prohibit slavery in any territory taken from Mexico as a result of the Mexican-American War. Representative David Wilmot introduced the measure that became known as the Wilmot Proviso, while Hamlin introduced a proviso of his own. Neither measure succeeded.
In 1848 Hamlin won election to the U.S. Senate. Troubled by the Democrats' increasingly pro-slavery stance, he nonetheless maintained his party loyalty until 1856. That year Maine Republicans persuaded him to become their gubernatorial candidate. After his election he resigned from the Senate to serve as governor of Maine, but left that post after less than two months to return to the Senate. In 1860 Hamlin successfully ran with Abraham Lincoln on the Republican presidential ticket. Although as vice president Hamlin ably presided over the Senate, he failed to win renomination four years later when the Republicans chose the war Democrat Andrew Johnson as Lincoln's running mate. In 1868 Hamlin was reelected to the Senate, where he served for 12 years. Following a brief period from 1881 to 1882 as U.S. minister to Spain, he retired from public life. Hamlin died in Bangor, Maine, in 1891.