In 1856 Julian was a delegate to the convention in Pittsburgh, that established the Republican Party. Julian served as chairman of the committee on national organization. In 1860 he was elected as a Republican to the Thirty-seventh Congress, and won re-election in the Thirty-eighth, Thirty-ninth, Fortieth, and Forty-first Congresses, serving from 1861 to 1871. Julian, among the most radical of the U.S. House Republicans, was an ardent abolitionist who also became known for his support of civil rights, women's suffrage, and land reform. Appointed to the congressional Committee on Public Lands in 1861, he also served as its chairman from 1863 to 1871. In addition, Julian was chairman of the Expenditures in the Navy Department (Thirty-ninth Congress).