Guevara helped carry out that revolution before attempting to foment similar uprisings elsewhere around the world, which helped make him an enemy of the U.S. Eventually, in 1967, C.I.A.-assisted Bolivian forces captured Guevara in Bolivia and executed him.

Nellie Connally, the First Lady of Texas who was riding in the front seat of the president's car, turned herself around and said, "Mr. President, you can't say Dallas doesn't love you."

President Kennedy's reply were his last words: "No, you certainly can't."

Seconds later, the fatal shot was fired.

On July 12, 1967, an act of police brutality against an African-American man in Newark, N.J. sparked riots throughout the city that would last for six days and leave 26 dead and hundreds injured.

Pictured: Kennedy (right), Monroe, and Kennedy's brother Robert backstage just after Monroe's performance. This is one of the few photos of Monroe and Kennedy together.

Ultimately cooler heads prevailed and both sides agreed to back their nuclear weapons farther away from the enemy's borders.

Pictured: A U.S. navy aircraft flies above a Soviet freighter carrying two bomber planes in late 1962.

In Berlin, Kennedy hoped to underline U.S. support for all people on the non-communist side of the world's great political divide, famously declaring "Ich bin ein Berliner" ("I am a citizen of Berlin"), which many incorrectly mistranslated as Kennedy proclaiming himself to be a jelly doughnut.

Artists like these had come to represent the voice of both the younger generation and highlight the plight of nation's oppressed through verse -- a trend that would only grow as the decade went on.

The suit remained out of public view in the National Archives in Maryland, together with an unsigned note reading "Jackie's suit and bag worn Nov. 22, 1963" until 2103. Its precise location is kept a secret. It was never cleaned.

Ruby told several witnesses immediately after shooting Oswald that he was trying to help the city of Dallas "redeem" itself in the public's eye, and spare "...Mrs. Kennedy the discomfiture of coming back to trial."

As Martin Luther King Jr. (left) was leaving a news conference, Malcolm X (right) stepped out of the crowd, extended his hand, and smiled.

"Well, Malcolm, good to see you," King said.

"Good to see you," X replied.

The gaggle of photographers surrounding the men took photos to immortalize the historic moment that lasted all of about one minute.

The famous 1965 Mondrian Collection by French designer Yves Saint Laurent took an innovative approach to fashion by combining classical Western forms with the aesthetics of modernist fine art.

Today, some of these dresses themselves are displayed at museums around the world.

The U.S. had just begun bombing operations and troop deployment in Vietnam, for the first time escalating in earnest the conflict that would make the 1960s a truly bloody decade.

Ali's courage both in and out of the ring would come to define the decade.

To contain the riots, the LAPD needed nearly 4,000 members of the California Army National Guard. In total, the riots resulted in 34 deaths and $40 million in property damage.

While they differed in approach, the two held each other in high esteem. As King later wrote of Johnson: "His approach to the problem of civil rights was not identical with mine — nor had I expected it to be. Yet his careful practicality was, nonetheless, clearly no mask to conceal indifference. His emotional and intellectual involvement was genuine and devoid of adornment. It was conspicuous that he was searching for a solution to a problem he knew to be a major shortcoming in American life."

After a failed career as a pornographer in Mexico, Ray had returned to the U.S. -- where he was wanted for escaping prison -- to take dance and bartending lessons before setting in motion his plan to kill King.

Ultimately, Ray's crimes earned him 99 years in prison, where he died in 1998 at age 70.

Washington, D.C. (pictured) saw the worst of it. Over the five days following King's death, rioters burned more than 1,000 buildings, causing about $27 million in damage and prompting President Johnson to call in 13,600 federal troops.

Pictured: American soldiers burn a Viet Cong base in My Tho on April 5, 1968.

The surprise attack on nearly 100 targets in South Vietnam marked a turning point in favor of the communists.

Pictured: Demonstrators rally outside the White House.

In the end, Soviet forces withdrew and granted Czechoslovakia some freedoms, but the country nevertheless remained under Soviet control, with future leaders tightening back up the restrictions that had been briefly loosened in 1968.

Shepard became the first American, and the second person ever, to travel into space. He was also the first to manually control a spacecraft.

After the assassination of John F. Kennedy five years earlier, many took the killing of his brother as a sign that, by 1968, the U.S. had truly reached its breaking point.

Soon after debuting in 1967, the revolutionary production -- noted for its controversial use of rock music, its embrace of the sexual revolution, and portrayal of drug use -- became a cultural touchstone of the era whose legacy lives on to this day.

Decades of LGBT mistreatment helped fuel what transpired at Stonewall. Soon after the riots, activist groups formed in New York and around the country, and today the event is widely recognized as the start of the LGBT rights movement in the U.S.

Astronauts Neil Armstrong and Edward "Buzz" Aldrin (pictured) walked the surface of the moon for two minutes and 34 seconds -- and in that brief time, made history like few others before or since.

The Woodstock Music & Art Fair ran from Aug. 15 to Aug. 18, 1969, but its impact reverberates to this day.