Labour government, 1974–1979
In March 1976, having just turned sixty years old, Wilson resigned as Prime Minister, ending his leadership of the Labour Party after thirteen years, and a total of nearly eight years as Prime Minister. He was replaced by James Callaghan, who had held senior government positions during both of Wilson's ministries, and had served as a Shadow Cabinet member in the early-1960s.
James Wilson (Secretary of Agriculture)
Wilson rose to national prominence in early 1897 when newly elected President William McKinley nominated him as his Secretary for Agriculture. During sixteen consecutive years of Republican administrations, Presidents McKinley, Theodore Roosevelt and William Howard Taft retained him in that position. It was not until March 1913, following the election of a Democratic president (Woodrow Wilson) that Wilson left that office. In all, Wilson served as Secretary of Agriculture from March 6, 1897 to March 5, 1913 — the longest duration served by any American cabinet official. The length of Wilson's tenure is attributed to not only the same political party occupying the White House in three consecutive administrations, but also the similarity in political philosophy among the three Presidents under which Wilson served. Given the state of national politics which developed in the 20th and 21st centuries, it is unlikely any Cabinet member will exceed Wilson's mark.