<P> The cause of Zachary Taylor's death was fully established in 2001 . Almost immediately after his death, rumors began to circulate that Taylor was poisoned by pro-slavery Southerners, and similar theories persisted into the twentieth century . The remains were exhumed and transported to the Office of the Kentucky Chief Medical Examiner on June 17, 1991 . Neutron activation analysis conducted at Oak Ridge National Laboratory revealed no evidence of poisoning, as arsenic levels were too low . The analysis concluded Taylor had contracted "cholera morbus, or acute gastroenteritis", as Washington had open sewers, and his food or drink may have been contaminated . </P> <P> Taylor was interred in the Public Vault of the Congressional Cemetery in Washington, D.C. from July 13, 1850 to October 25, 1850 . (It was built in 1835 to hold remains of notables until either the grave site could be prepared or transportation arranged to another city .) His body was transported to the Taylor Family plot where his parents are buried, on the old Taylor homestead plantation known as' Springfield' in Louisville, Kentucky . </P> <P> The assassination of Abraham Lincoln took place on Good Friday, on April 14, 1865, as the American Civil War was drawing to a close . The assassination occurred five days after the commanding General of the Army of Northern Virginia, Robert E. Lee, surrendered to General Ulysses S. Grant and the Army of the Potomac . Lincoln was the first American president to be assassinated, though an unsuccessful attempt had been made on Andrew Jackson 30 years before in 1835 . </P> <P> The assassination of Lincoln was planned and carried out by the well - known stage actor John Wilkes Booth, a Confederate sympathizer, vehement in his denunciation of Lincoln, and a strong opponent of the abolition of slavery in the United States . Booth and a group of co-conspirators originally plotted to kidnap Lincoln, but later planned to kill him, Vice President Andrew Johnson, and Secretary of State William H. Seward in a bid to help the Confederacy's cause . (Vice President Johnson's assailant did not carry out his part of the plan, and Johnson succeeded Lincoln as President .) </P>

Who was the first president to be killed in office