 The earliest known photograph of a U.S. First Lady is joining the permanent collection at the National Portrait Gallery. The photo of former First Lady Dolly Madison likely dates from 1846 when she was in her late 70s. The National Portrait Gallery bought it at auction last month for just over $450,000. Dolly Madison is credited with creating the role of First Lady as it's known today. The gallery already owns the first known photograph of a U.S. President.