To write his 5 volume biography of George Washington, John Marshall had been given all of Washington's personal and public papers by Bushrod Washington, another U.S. Supreme Court justice who was the nephew of George Washington and had inherited the papers. John Marshall had previously fought in the American Revolution under George Washington. After the Revolution ended, he became the leading lawyer in Virginia and was eventually appointed both Secretary of State and Chief Justice of the U.S. Supreme Court by John Adams, both positions which he briefly held jointly. As Secretary of State, John Marshall administered the presidential oath of office to newly elected President Thomas Jefferson, a distant cousin of John Marshall's. Despite being cousins, Marshall and Jefferson became hated rivals, with John Marshall being the principal spokeman of the Federalists and preserver of the traditions of George Washington and with Thomas Jefferson being the leader of the newly-formed opposition Democrat-Republican Party and an opponent of many of the policies of the Federalists. Ironically, despite Jefferson's opposition to a strong federal government, Jefferson ended up signing the Louisiana Purchase which doubled the size of the United States. Meanwhile, the political philosophy of George Washington lived on through John Marshall, who was our longest serving Chief Justice of the Supreme Court and who is credited with establishing the judiciary as the third principal branch of our govenment with his decision in Marbury v. Madison which stated that only the U.S. Supreme Court had the power to decision what laws were constitutional (i.e. judicial review).