The First Ladies of the United States are the women who have served as the hostesses of the White House. The position is traditionally filled by the wife of the president of the United States, but, on occasion, the title has been applied to women who were not presidents’ wives, such as when the president was a bachelor or widower. Following Barack Obama's first inauguration on January 20, 2009, his wife, Michelle Obama, became the forty-sixth official First Lady. There are five living former First Ladies: Rosalynn Carter, wife of Jimmy Carter; Nancy Reagan, widow of Ronald Reagan; Barbara Bush, wife of George H. W. Bush; Hillary Rodham Clinton, wife of Bill Clinton; and Laura Bush, wife of George W. Bush. The first First Lady was Martha Washington, married to George Washington. The wives of four Presidents died before their husbands were sworn into office but are still considered First Ladies by the White House and National First Ladies' Library: Martha Jefferson, Rachel Jackson, Hannah Van Buren (pictured), and Ellen Lewis Herndon Arthur. (Full list...)