Given the question: Formulate an answer to this elaborate question: William McKendree Gwin (October 9, 1805 September 3, 1885) was an American medical doctor and politician, serving in elected office in Mississippi and California, in California he shared the distinction, along with which American explorer, politician, and soldier who, in 1856, became the first candidate of the anti-slavery Republican Party for the office of President of the United States?
The answer is:
John Charles Fremont