Margaret Mackall Smith Taylor ( September 21 , 1788 - August 14 , 1852 ) , wife of Zachary Taylor , the President of the United States . She was First Lady of the United States from 1849 to 1850 . Margaret Mackall Smith `` Peggy '' Taylor ( September 21 , 1788 -- August 14 , 1852 ) , wife of Zachary Taylor , was First Lady of the United States from 1849 to 1850 .