However, the death penalty under federal law is applicable in every state. Hanging is no longer used as a method of execution. The largest mass execution in the United States, of 38 Sioux Indians sentenced to death for engaging in massacres of American settlers, was carried out by hanging in Mankato, Minnesota in 1862. A total of 40 suspected Unionists were hanged in Gainesville, Texas in October 1862. On 7 July 1865, four people involved in the assassination of President Abraham Lincoln—Mary Surratt, Lewis Powell, David Herold, and George Atzerodt—were hanged at Fort McNair in Washington, D.C. The last public hanging in the United States took place on 14 August 1936, in Owensboro, Kentucky. Rainey Bethea was executed for the rape and murder of 70-year-old Lischa Edwards. The execution was presided over by the first female sheriff in Kentucky, Florence Shoemaker Thompson. In California, Clinton Duffy, who served as warden of San Quentin State Prison between 1940 and 1952, presided over ninety executions. He began to oppose the death penalty and after his retirement he wrote a memoir entitled "Eighty-Eight Men and Two Women" in support of the movement to abolish the death penalty. The book documents several hangings gone wrong and describes how they led his predecessor, Warden James B. Holohan, to persuade the California Legislature to replace hanging with the gas chamber in 1937. Various methods of capital punishment have been replaced by lethal injection in most states and the federal government. Many states that offered hanging as an option have since eliminated the method. Condemned murderer Victor Feguer became the last inmate to be executed by hanging in the state of Iowa on 15 March 1963. Hanging was the preferred method of execution for capital murder cases in Iowa until 1965, when the death penalty was abolished and replaced with life imprisonment without parole. Barton Kay Kirkham was the last person to be hanged in Utah, preferring it over execution by firing squad. No subsequent inmate in Utah had been hanged by the time the option was replaced with lethal injection in 1980. Laws in Delaware were changed in 1986 to specify lethal injection, except for those convicted before 1986 (who were still allowed to choose hanging). If a choice was not made, or the convict refused to choose injection, then hanging would become the default method. This was the case in the 1996 execution of Billy Bailey, the most recent hanging in American history; since then, no Delaware prisoner fit the category, and the state's gallows were later dismantled.