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?

full_context: Document 1: John Quincy Adams: John Quincy Adams ( ; July 11, 1767 – February 23, 1848) was an American statesman who served as a diplomat, United States Senator, member of the House of Representatives, and the sixth President of the United States from 1825 to 1829. He was a member of the Federalist, Democratic-Republican, National Republican, and later the Anti-Masonic and Whig parties. He was the son of President John Adams and Abigail Adams and thus contributed to the formation of the Adams political family.
Document 2: Jefferson Davis: Jefferson Davis (born Jefferson Finis Davis; June 3, 1808 – December 6, 1889) was an American politician who served as the President of the Confederate States from 1861 to 1865. He was a member of the Democratic Party who represented Mississippi in the United States Senate and the House of Representatives prior to becoming president of the Confederacy. He was the 23rd United States Secretary of War, serving under U.S. President Franklin Pierce from 1853 to 1857.
Document 3: William Gunn (physician): William Gunn (1855–1922) was one of Florida's first black doctors. He began his career working as a driver for a doctor at the Knott House. Gunn was born in Leon County, Florida in 1855. He was mentored by Dr. Betton, a white physician who financed Gunn's education at Meharry Medical College after Gunn came to work for him as a driver.
Document 4: Fremont Peak (Wyoming): Fremont Peak is the third highest peak in Wyoming and straddles the boundary between Fremont and Sublette counties. It is named for American explorer John C. Fremont who climbed the peak with Charles Preuss and Johnny Janisse on August 13 to August 15, 1842. Kit Carson had been with the climbing party on its first attempt at the peak, but had gone back for supplies the day Fremont and his men reached the summit. Carson is thought by some to have been the first to climb neighboring Jackson Peak. At that time, Fremont Peak was mistakenly thought to be the highest mountain in the Rocky Mountains, although there are actually over 100 higher peaks in the range.
Document 5: John C. Frémont: John Charles Frémont or Fremont (January 21, 1813July 13, 1890) was an 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. During the 1840s, when he led four expeditions into the American West, that era's penny press and admiring historians accorded Frémont the sobriquet "The Pathfinder".
Document 6: William B. Ide: William Brown Ide (March 28, 1796 – December 19 or 20, 1852) was a California pioneer who headed the short-lived California Republic in 1846.
Document 7: William M. Gwin: 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 John C. Frémont, of being the state's first U.S. senators. Before, during, and after the Civil War, Gwin was well known in California, Washington, DC, and in the south as a determined southern sympathizer.
Document 8: George Henry Williams: George Henry Williams (March 26, 1823April 4, 1910) was an American judge and politician. He served as Chief Justice of the Oregon Supreme Court, was the 32nd Attorney General of the United States, and was elected Oregon's U.S. Senator, and served one term. Williams, as U.S. Senator, authored and supported legislation that allowed the U.S. military to be deployed in Reconstruction southern states to allow for an orderly process of readmittance into the United States. Williams was the first presidential Cabinet member to be appointed from the Pacific Coast. As attorney general under President Ulysses S. Grant, Williams continued the prosecutions that shut down the Ku Klux Klan. He had to contend with controversial election disputes in Reconstructed southern states. President Grant and Williams legally recognized P. B. S. Pinchback as the first African American state governor. Williams ruled that the "Virginius", a gun-running ship captured by Spain during the Virginius Affair, did not have the right to bear the U.S. flag. However, he argued that Spain did not have the right to execute American crew members. Nominated for Supreme Court Chief Justice by President Grant, Williams failed to be confirmed by the U.S. Senate primarily due to Williams' removal of A. C. Gibbs United States District Attorney at Portland, Oregon.
Document 9: Lewis Cass: Lewis Cass (October 9, 1782June 17, 1866) was an American military officer, politician, and statesman. He represented Michigan in the United States Senate and served in the Cabinet of Andrew Jackson and James Buchanan. He was also the 1848 Democratic presidential nominee and a leading spokesman for the Doctrine of Popular Sovereignty, which held that the people in each territory should decide whether to permit slavery.
Document 10: Edwin James (scientist): Edwin P. James (27 August 1797 – 28 October 1861) was a 19th-century American botanist, geographer and geologist who explored the American West. James completed the first recorded ascent of Pikes Peak. In addition to his explorations, James was also known for his time spent aiding in creating relationships with the Native Americans as well as helping African Americans to escape slavery. James was primarily known for his work serving as a botanist and geologist during Thomas Say's expedition from Pittsburgh to the Rocky Mountains and was in charge of charting and taking note of the new discoveries on the journey. His work on the expedition was similar to that of Alexander Von Humboldt's.
Document 11: John Wallace Crawford: John Wallace ("Captain Jack)" Crawford (1847–1917), known as "The Poet Scout", was an American adventurer, educator, and author. "Captain Jack" was a master storyteller about the Wild West and is known in American history as one of the most popular performers in the late nineteenth century. His daring ride of 350 miles in six days to carry dispatches to Fort Laramie for the "New York Herald", to tell the news of the great victory by Gen. George Crook against the village of Chief American Horse at the Battle of Slim Buttes during the Great Sioux War of 1876-1877, made him a national celebrity.
Document 12: John G. Downey: John Gately Downey (June 24, 1827 – March 1, 1894) was an Irish-American politician and the seventh governor of California from January 14, 1860 to January 10, 1862. Until the election of Arnold Schwarzenegger in 2003, Downey was the only governor of California to be born outside the United States. Downey was also the first man from Southern California to be elected as governor.
Document 13: Kit Carson: Christopher Houston Carson (December 24, 1809 – May 23, 1868), better known as Kit Carson, was an American frontiersman. He was a mountain man (fur trapper), wilderness guide, Indian agent, and U.S. Army officer. Carson became a frontier legend in his own lifetime via biographies and news articles. Exaggerated versions of his exploits were the subject of dime novels.
Document 14: William Winter (politician): William Forrest Winter (born February 21, 1923) is a retired American politician who served as the 58th Governor of Mississippi from 1980 to 1984. A Democrat, he is known for his strong support of public education, freedom of information, racial reconciliation, and historic preservation. Winter is best remembered for the passage of the Mississippi Education Reform Act. The law was the first serious attempt at improving state education in over 20 years and established public kindergartens. The Winter administration also successfully rewrote the state public utilities law when the legislature passed the Public Utilities Reform Act.
Document 15: William S. Barry: William S. Barry (born William Taylor Sullivan Barry; December 10, 1821 – January 29, 1868) was an American politician who served as member of the Provisional Congress of the Confederate States from Mississippi. Prior to this Barry served as a member of the U.S. House of Representatives from Mississippi's 2nd congressional district.
ground_truth: John Charles Frémont