Massachusetts became the sixth state to join the Union on February 6, 1788. Massachusetts's first two senators, Tristram Dalton and Caleb Strong, took office on March 4, 1789. The state's longest-serving senators include George Hoar (1877–1904), Henry Cabot Lodge, Sr. (1893–1924), and Edward Kennedy (1962–2009). Among those who rose to leadership positions are Lodge and Leverett Saltonstall, both of whom served as Republican Conference chairmen. Four men from Massachusetts have served as vice president of the United States and therefore as the Senate's constitutional president or presiding officer: John Adams, Elbridge Gerry, Henry Wilson, and Calvin Coolidge. John F. Kennedy became the second sitting senator to be elected president of the United States.