WordNet sense 1 (United States explorer who (with Meriwether Lewis) led an expedition from St. Louis to the mouth of the Columbia River; Clark was responsible for making maps of the area (1770-1838)):

William Clark

WordNet sense 2 (United States general who was Allied commander in Africa and Italy in World War II and was commander of the United Nations forces in Korea (1896-1984)):

Mark Clark, Mark Wayne Clark

WordNet sense 3 (United States psychologist (born in Panama) whose research persuaded the Supreme Court that segregated schools were discriminatory (1914-)):

Kenneth Bancroft Clark, Kenneth Clark

WordNet sense 4 (Canadian politician who served as prime minister (1939-)):

Charles Joseph Clark, Joe Clark