Which event occurred in 1963 and caused the United States to experience a major transition?

the election of President Johnson

the assassination of President Kennedy

the passage of the Economic Opportunity Act

the signing of the Civil Rights Act

The event that occurred in 1963 and caused the United States to experience a major transition was the assassination of President Kennedy.

Explanation:

The assassination of John F. Kennedy, thirty-fifth president of the United States, took place on Friday, November 22, 1963, in Dallas, Texas. Kennedy was mortally wounded by gunfire while circulating in the presidential car at Dealey Plaza. He was the fourth president of the United States murdered (with Abraham Lincoln, James Abram Garfield and William McKinley) and the eighth who died in the exercise of his functions.

Three official investigations concluded that Lee Harvey Oswald, an employee of the Texas School Book Depository store in Dealey Plaza, was the killer. One of them concluded that Oswald acted alone and another suggested that he acted with at least one other person. The murder is still subject to speculation, being the origin of a large number of conspiracy theories.

Answer: It was "the assassination of President Kennedy" that took place in 1963.

Explanation: This event caused the country to experience a major transition.