Adopted in 1967, the Twenty-fifth Amendment to the United States Constitution establishes the current line of succession to the Presidency, and creates the procedures for filling vacancies. The aim was to clarify Article II, Section 1, Clause 6, as that part of the Constitution was unclear.
The first time this became a major issue was in 1841, when President William Henry Harrison became the first U.S. President to die in office. Representative John Williams had previously suggested that the Vice President should become Acting President upon the death of the President. Vice President John Tyler concurred, asserting that he would need to succeed to the office of President, as opposed to only obtaining its powers and duties. Though Tyler became took the oath of President (precedent for full succession was established, became known as "Tyler Precedent"), nothing was done to amend the Constitution regarding the procedure.
When President Wilson suffered a stroke, no one officially assumed the Presidential powers and duties.
It was clear that a set of guidelines needed to be established.
In 1963, a proposal enabling Congress to enact legislation establishing a line of succession by Senator Kenneth Keating of New York based upon a recommendation by the American Bar Association in 1960 surfaced, but it never gained enough support.
On January 6, 1965, Senator Birch Bayh proposed in the Senate and Representative Emanuel Celler proposed in the House of Representatives what would become the Twenty-fifth Amendment. Their proposal provided a way to not only fill a vacancy in the office of the President by the Vice President, but also how to fill the office of the Vice President before the next presidential election (something Keating's proposal failed to address).
The Twenty-sixth Amendment establishes the voting age at the age of 18 (rather than 21 as it was previously). The amendment was proposed in 1971, in an attempt to respond to student activism against the Vietnam War. Originally, President Nixon had signed a law making the voting age 18, but a number of states challenged the law, and under pressure the amendment was proposed and ratified.
The slogan, "Old enough to fight, old enough to vote," which surfaced as far back as World War II, finally had won its fight. Arguments of various viewpoints regarding the wisdom of this amendment continue to this day.
The Twenty-seventh Amendment prohibits any law that increases or decreases the salary of members of the Congress from taking effect until the start of the next set of terms of office for Representatives. Ratified in 1992, the proposal remained in place for 203 years after its initial submission in 1789.