Abstract: William Henry Crook (October 15, 1839 - March 13, 1915) was one of President Abraham Lincoln's bodyguards in 1865. After Lincoln's assassination (while Crook was off duty), he continued to work in the White House for a total of more than 50 years, serving 12 Presidents.Crook set his memoirs down on paper in the book Through Five Administrations: Reminiscences of Colonel William H. Crook, Body-Guard to President Lincoln, compiled and edited by Margarita Spalding Gerry and published for the first time in 1910. There are six administrations covered, however, from Lincoln to Chester A. Arthur, although James A. Garfield and Arthur are dealt with in a single chapter.Lincoln's Last Day is one of the most interesting reminiscences by William Henry Crook and a fundamental direct testimony of the last day of life of one of the greatest Presidents in the history of the United States of America. It was published on the Harper's Monthly Magazine in September 1907.