1846 daguerreotype of Dolley Madison, the first US first lady, acquired by the Smithsonian's National Portrait Gallery for $456,000.

The Smithsonian's National Portrait Gallery has acquired the oldest known photograph of a US first lady, believed to be a daguerreotype of Dolley Madison taken in 1846. It is the first photograph of a first lady; Dolley Madison was the wife of the fourth US president, James Madison, and was "considered by many to have invented the role of First Lady." The daguerreotype was purchased for $456,000 at a Sotheby's auction in June.