America. The land of opportunity where "the son of a single mom can be president of the greatest nation on Earth," as President Obama put it in his State of the Union speech Tuesday.

Of course he was referring to his favorite subject — himself — as if he'd blazed a new trail of opportunity.

But in fact, the story of presidents being raised by single mothers is as old as America itself. George Washington's mother, Mary, became a widow when he was 11. Thomas Jefferson was raised by his mother, Jane Randolph Jefferson, after his father died when he was 14.

And Andrew Jackson's father, like Bill Clinton's, died before he was born.