Historians have commonly used the term “White House hostess” for women who performed the First Lady’s social duties for an unmarried president. More recently, they have been considered as First Ladies in their own right, and are listed as such.

James Buchanan recruited his niece, the very talented Harriet Lane, to act as official hostess while he was ambassador to Great Britain. She stayed on as First Lady when he became President. By most accounts, the country would have been better off if she had taken over his duties as well.

Buchanan was the only president who never married, but several others have been single for at least part of their terms.

Chester Arthur, a widower, was single throughout his term. His sister, Mary Arthur McElroy, served as First Lady during his term.

Grover Cleveland, also widowed, married midway through his first term. His sister, Rose Cleveland, served as First Lady in the meantime.

Woodrow Wilson’s first wife, Ellen Axson Wilson, died during his first term. Their daughter, Margaret Wilson, was officially White House hostess and therefore First Lady, until Wilson re-married about a year later.

Woodrow Wilson was the last President who was single at any point during his term. Cleveland was the last to be elected while single.