On the night that John Wilkes Booth shot and killed Abraham Lincoln, the legislation to create the United States Secret Service sat on the President’s desk in the White House. At first, the organization primarily pursued counterfeiters, which at the time accounted for as much as 1/3 of all paper bills in circulation, and over time also combated other federal crimes including murder, robbery, and racketeering. After the assassination of President William McKinley in September of 1901—the third Presidential assassination in less than forty years—the Secret Service also undertook the responsibility of providing personal protection for the Chief Executive, his immediate family, and visiting or foreign dignitaries.
In the early 60s, the Cold War between West and East dominated the political landscape. While America relied on South Vietnam to resist the draw of Communism spreading down from the north, South Vietnamese president Ngo Dinh Diem, a Roman Catholic, carried out a policy of repression against the Buddhist majority of the state. As time went on, the Diem administration met Buddhist protests with increasing levels of force, even as American President John F. Kennedy prepared to pull roughly 16,000 US soldiers out of South Vietnam and strike a treaty with the North. Soon, Diem's own generals plotted to overthrow him, to which Diem responded by declaring martial law.
John Wilkes Booth’s assassination of President Lincoln was actually one of three elements in the planned attack on April 14, 1865. Booth had learned that Lincoln was to attend the play Our American Cousin at Ford's Theater, and, being a well-known youngest member of a famous acting family, was very familiar with the interior of the building. He scouted out Ford's Theater hours before Lincoln's arrival, and planned his attack meticulously. Booth carved a peephole in the door to the Presidential Box and rigged up a way to jam it shut once he was inside.