Final answer:
John Wilkes Booth assassinated President Abraham Lincoln due to his support for the rights of black citizens and Lincoln's alignment with the Union, which countered Booth's Confederate sympathies and white supremacist views.
Step-by-step explanation:
John Wilkes Booth, a staunch defender of the Confederacy and white supremacy, was incensed by President Abraham Lincoln's support for the rights of black citizens.
After Lincoln's speech expressing support for enfranchising black Americans, Booth, who had previously plotted to kidnap the president, decided that he had to assassinate him.
Booth's deep-seated beliefs and his unwavering commitment to the Confederacy drove him to commit the act of assassination on April 14, 1865, at Ford's Theater, profoundly affecting the nation and altering the course of history.