John F. Kennedy, 1957. (Credit: Hank Walker/The LIFE Picture Collection/Getty Images)

He and Jackie Kennedy had four children.

In addition to Caroline and John, Jr., the Kennedys had two other children. In 1956, Jackie gave birth to a stillborn girl whom the couple intended to name Arabella, and on August 7, 1963, Patrick Bouvier Kennedy was born five-and-a-half weeks early. The baby weighed under five pounds and died two days later from a pulmonary disease. The bodies of the two children were removed from Massachusetts in 1963 to be next to their father in Arlington National Cemetery.

Kennedy received last rites three times before his presidency.

Kennedy suffered from poor health his entire life and, fearing imminent death, America’s first Catholic president received the sacramental last rites of the church on three occasions. On a trip to England in 1947, Kennedy fell ill and was given perhaps a year to live after being diagnosed with Addison’s disease, a rare disorder of the adrenal glands. Returning to America aboard the Queen Mary, Kennedy was so ill that a priest was summoned to administer last rites. He received the sacrament again in 1951 after suffering from an extremely high fever while traveling in Asia and in 1954 after he slipped into a coma from an infection after surgery to address his chronic back problems.

The Army medically disqualified Kennedy from service

In the months before the United States entered World War II, Kennedy attempted to enlist in the military, but his intestinal and back problems caused him to fail the physical examinations for both the Army’s and Navy’s officer candidate schools. Using his father’s connections, however, the future president was admitted to the Navy in October 1941. As a commanding officer of PT-109, he became a wartime hero after helping his crewmates survive the gunboat’s 1943 sinking.

He won a Pulitzer Prize.

Kennedy authored his first book, “Why England Slept,” at age 22, and in 1945 he spent a few months as a newspaper correspondent for William Randolph Hearst’s newspapers covering the United Nations conference in San Francisco and the aftermath of World War II in Europe. In 1957, a Pulitzer Prize in biography was awarded to Kennedy for “Profiles in Courage,” although there has since been controversy as to how much of the book was ghostwritten by his aide Theodore Sorensen.

Kennedy briefly attended Princeton University.

Prior to his enrollment at Harvard University, the future president in 1935 began his undergraduate career at another Ivy League institution, Princeton University. His stint there was brief. A gastrointestinal illness forced him to leave Princeton after only two months, and after convalescing he transferred to Harvard.

He donated his congressional and presidential salary to charity.

Kennedy’s father built a family fortune, and when the young politician entered Congress in 1947, he earned sufficiently ample annual income from trusts established by his father that he decided to donate his entire legislative salary to various charities. Kennedy quietly maintained the practice as president after becoming the richest man to ever take the oath of office.

Kennedy installed a secret taping system in the White House.

Richard Nixon was not the first president to record his private White House conversations. In the summer of 1962, Kennedy secretly installed a taping system in the Oval Office and Cabinet Room that transmitted recordings to a reel-to-reel tape recorder in the White House basement. The president likely installed the system to aid him in writing his future memoir, and it captured many historical discussions between Kennedy and his staff, including discussions during the Cuban Missile Crisis.

Kennedy proposed a joint Soviet mission to the moon.

Although Kennedy famously challenged the country in the first months of his presidency to land a man on the moon by the end of the 1960s, by September 1963 he had such concerns about the space program’s high cost that he proposed partnering with the Soviet Union on a joint expedition to the moon. “Why,” he asked in an address to the United Nations General Assembly, “should man’s first flight to the moon be a matter of national competition? Why should the United States and the Soviet Union, in preparing for such expeditions, become involved in immense duplications of research, construction and expenditure?”

There were rumors that he considered dropping Lyndon Johnson from the 1964 ticket.

With more than a year before the 1964 presidential election, rumors swirled that Kennedy was considering replacing Johnson as his running mate with Florida Senator George Smathers, North Carolina Governor Terry Sanford or another Democrat. Kennedy’s secretary, Evelyn Lincoln, wrote in her 1968 memoir that the president mentioned a possible switch to her three days before his death, and hours before the assassination, the November 22, 1963, edition of the Dallas Morning News printed an interview with Nixon, who was in the city on business, with the headline: “Nixon Predicts JFK May Drop Johnson.”

Kennedy feared running for re-election against Mitt Romney's father.

When evaluating prospective Republican candidates for the 1964 presidential campaign, Kennedy welcomed the prospect of running against Arizona Senator Barry Goldwater, who ultimately received his party’s nomination, but he was concerned about the prospects of facing more moderate Michigan Governor George Romney, father of the 2012 Republican presidential nominee. “The one fellow I don’t want to run against is Romney. That guy could be tough” he privately confided to a friend in 1963.