Thomas J. Manton was born in Manhattan and attended private Catholic schools in Queens and Brooklyn before becoming a flight navigator in the U.S. Marine Corps from 1951 to 1953. He graduated from St. John’s University in 1958 and was a member of the New York City Police Department from 1955 to 1960. He was admitted to the bar in 1963 and became a practicing attorney. In 1970, Manton was elected to the New York City Council, where he served from 1970 until 1984; he was then elected as a Democratic representative to Congress from 1985 until 1998.

As co-chairman of the Congressional Ad Hoc Committee on Irish Affairs, Manton helped persuade President Bill Clinton to meet with Gerry Adams, president of Sinn Fein, the political arm of the Irish Republican Army, in 1995. Manton also was the chairman of the Queens Democratic Organization for 20 years.