Many presidents of the United States have written autobiographies about their presidencies and/or (some periods of) their life before their time in office. Some 19th-century U.S. presidents who wrote autobiographies are James Buchanan and Ulysses S. Grant, though Grant's autobiography is about his time as general during the American Civil War and not about his presidency. Presidential memoir has proved to be a lasting and popular genre â every president who survived to the end of their term from Calvin Coolidge to Barack Obama has published one after leaving office, and more recent entries have earned their authors tens of millions of dollars in royalties. In addition to ensuring financial security, presidential autobiographies are also written to defend or rehabilitate presidential legacies.