Original: Sarah Childress Polk ( September 4 , 1803 -- August 14 , 1891 ) was the wife of the 11th President of the United States , James Polk , and the 12th woman to serve as First Lady .
Simplified: Sarah Childress Polk ( September 4 , 1803 - August 14 , 1891 ) was the wife of the US President James K. Polk .