The primary responsibility of the Vice President of the United States is to be ready at a moment's notice to assume the Presidency if the President is unable to perform his duties. This can be because of the President's death, resignation, or temporary incapacitation, or if the Vice President and a majority of the Cabinet judge that the President is no longer able to discharge the duties of the presidency.
The Vice President is elected along with the President by the Electoral College — each elector casts one vote for President and another for Vice President. Before the ratification of the 12th Amendment in 1804, electors only voted for President, and the person who received the second greatest number of votes became Vice President.
The Vice President also serves as the President of the United States Senate, where he or she casts the deciding vote in the case of a tie. Except in the case of tiebreaking votes, the Vice President rarely actually presides over the Senate. Instead, the Senate selects one of their own members, usually junior members of the majority party, to preside over the Senate each day.
Of the 45 previous Vice Presidents, nine have succeeded to the Presidency, and four have been elected to the Presidency in their own right. The duties of the Vice President, outside of those enumerated in the Constitution, are at the discretion of the current President. Each Vice President approaches the role differently — some take on a specific policy portfolio, others serve simply as a top adviser to the President.
The Vice President has an office in the West Wing of the White House, as well as in the nearby Eisenhower Executive Office Building. Like the President, he also maintains an official residence, at the United States Naval Observatory in Northwest Washington, D.C.
Located on the grounds of the United States Naval Observatory (USNO), the white 19th Century house at Number One Observatory Circle in northwestern Washington, D.C., was built in 1893. Originally intended for the superintendent of the USNO, the house was so lovely that in 1923, the chief of naval operations kicked out the superintendent so he could move in himself. Historically, Vice Presidents and their families lived in their own homes, but the cost of securing these private residences grew substantially over the years. Finally, in 1974, Congress agreed to refurbish the house at the Naval Observatory as a home for the Vice President.
Three years passed before any Vice President actually lived at Number One Observatory Circle. Vice President Gerald Ford acceded to the Presidency before he could use the home, and his Vice President, Nelson Rockefeller, only used it for entertaining. Walter Mondale was the first Vice President to move into the home. It has since been home to the families of Vice Presidents Bush, Quayle, Gore, and Cheney. Vice President and Dr. Biden currently reside there.
Vice Presidents have welcomed countless guests to the residence, including foreign leaders and dignitaries. Still, the Naval Observatory has continued to operate. Scientists observe the sun, moon, planets and selected stars, determine and precisely measure the time, and publish astronomical data needed for accurate navigation.