John Charles Fremont
John Charles Frémont (January 21, 1813 – July 13, 1890), was an American military officer, explorer, the first candidate of the Republican Party for the office of President of the United States, and the first presidential candidate of a major party to run on a platform in opposition to slavery.
Benson John Lossing, ed. Harper's Encyclopedia of United States History (vol. 3) (New York, NY: Harper and Brothers, 1912)