Julia Tyler(1820 - July 10, 1889)
Julia Gardiner married the widowed president, John Tyler, in 1844, which was the first time a president married while in office. She served as First Lady until the end of his term in 1845. During the Civil War, she lived in New York and worked to support the Confederacy. After she successfully persuaded Congress to grant her a pension, Congress passed a law giving pensions to other presidential widows.
Margaret Taylor(September 21, 1788 - August 18, 1852)
Margaret Mackall Smith Taylor was a reluctant First Lady. She spent most of the presidency of her husband, Zachary Taylor, in relative seclusion, giving rise to many rumors. After her husband died in office (of cholera), she refused to speak of her White House years.
While a teacher, Abigail Powers Fillmore taught her future husband, Millard Fillmore (president 1850 - 1853), and helped him develop his potential and enter politics. She remained an advisor, resenting and avoiding the typical social duties of a First Lady, preferring her books and music and discussions with her husband about the issues of the day, though failing to persuade her husband against signing the Fugitive Slave Act. She fell ill at the inauguration of her husband's successor and died soon after of pneumonia.
Jane Means Appleton Pierce married her husband, Franklin Pierce (president 1853 - 1857), despite her opposition to his already-fruitful political career. She blamed the death of three of their children on his involvement in politics; the third, died in a train wreck just before Franklin's inauguration. Abigail (Abby) Kent Means, her aunt, and Varina Davis, wife of Secretary of War Jefferson Davis, largely handled the hostess responsibilities of first ladies.
Harriet Lane Johnston(May 9, 1830 - July 3, 1903)
James Buchanan (president 1857 - 1861) was not married. His niece Harriet Lane, whom he adopted and raised after she was orphaned, carried out the hostess duties of a First Lady while he was president.
Mary Todd Lincoln
Mary Todd was a well-educated, fashionable young woman from a well-connected family when she met frontier lawyer Abraham Lincoln (president 1861 - 1865). Three of their four sons died before reaching adulthood; Mary had a reputation for being unstable, spending uncontrollably, and interfering in politics. In later life, her surviving son had her committed briefly, and America's first woman lawyer, Myra Bradwell, helped get her released.
Eliza McCardle Johnson married Andrew Johnson (president 1865 - 1869) and encouraged his political ambitions, while herself largely preferring to stay out of public view. She shared hostess duties at the White House with her daughter, Martha Patterson. She likely served informally as a political advisor to her husband during his political career.
Julia Dent Grant married Ulysses S. Grant and spent some years as an Army wife. When he left military service 1854 - 1861, the couple and their four children did not do particularly well. Grant was called back to service for the Civil War, and when he was president (1869 - 1877), Julia Grant enjoyed the social life and public appearances. After his presidency, they again fell on hard times, rescued by the financial success of her husband's autobiography. Her own memoir was not published until 1970.
Lucy Ware Webb Hayes was the first wife of an American president to have a college education, and she generally well-liked as First Lady. She was also known as Lemonade Lucy, for the decision she made with her husband Rutherford B. Hayes (president 1877 - 1881) to ban liquor from the White House, and she's also known for instituting the annual Easter egg roll on the lawn of the White House.