Garfield won election as a member of the U.S. House of Representatives while still a soldier in the Union army. He defeated his Democratic candidate D. B. Woods by a large margin even though he didn’t campaign for the position. President Abraham Lincoln, whom Garfield had supported in Ohio, encouraged Garfield to take the position.

He served as a U.S. congressman for seventeen years until he ran for president in 1880. He served as chairman of the Banking and Currency Committee and the Military Affairs Committee. In 1874, he became the House minority leader for the Republicans, as the Democrats were in the majority.