The youngest president in American history was not John F. Kennedy, as is often perceived given his youthful appearance and untimely death at the hands of a murderous assassin. Nor was it Barack Obama, whose first presidential campaign in 2008 found support among the nation's youth. It wasn't Bill Clinton, either, whose indiscretions with a White House intern nearly cost him his job. The youngest president, Theodore Roosevelt, was thrust into office following the assassination of President William McKinley in 1901. Roosevelt wrote in a proclamation to the American people on Sept. 14 of that year: "A terrible bereavement has befallen our people. The President of the United States has been struck down; a crime not only against the Chief Magistrate, but against every law-abiding and liberty-loving citizen." Our youngest president was only seven years older than the constitutional requirement that the White House occupant be at least 35 years old. Roosevelt's leadership ability, however, defied his youthful age. The Theodore Roosevelt Association notes: "Though he remains the youngest person ever to hold America’s highest office, Roosevelt was one of the best prepared to be president, entering the White House with a broad understanding of governmental and legislative processes and with executive leadership experience." Roosevelt was reelected in 1904, when he reportedly said to his wife: "My dear, I am no longer a political accident." All U.S. presidents have been at least 42 when they moved into the White House. Some of them have been decades older than that. The oldest president ever to take the White House, Donald Trump, was 70 when he took the oath of office. Here is a look at the nine men who were under 50 when they were sworn in.

Theodore Roosevelt Theodore Roosevelt was America's youngest president at 42 years, 10 months, and 18 days old when he was sworn into the presidency. Roosevelt was likely used to being the young guy in politics. He was elected to the New York State Legislature at the age of 23. That made him the youngest state lawmaker in New York at the time. Though Kennedy was the youngest president at the time of leaving office, Kennedy's untimely departure came by assassination. Roosevelt was the youngest to leave through the normal transition of power to the next president. At the time, Roosevelt was age 50 years, 128 days.

John F. Kennedy John F Kennedy takes the oath of office administered by Chief Justice Earl Warren. Getty Images/Hulton Archive John F. Kennedy is often mentioned as the youngest president ever. He took the presidential Oath of Office in 1961 at 43 years, 7 months, and 22 days old. While Kennedy isn't the youngest person to occupy the White House, he is the youngest person elected president. Roosevelt wasn't initially elected president and was vice president when McKinley was killed. Kennedy was, however, the youngest president to leave office at age 46 years, 177 days.

Bill Clinton Chief Justice William Rehnquist swears in President Bill Clinton in 1993. Jacques M. Chenet/Corbis Documentary Bill Clinton, a former governor of Arkansas, became the third-youngest president in U.S. history when he took the oath of office for the first of two terms in 1993. Clinton was 46 years, 5 months, and 1 day old at the time.

Ulysses S. Grant Brady-Handy Photograph Collection (Library of Congress) Ulysses S. Grant is the fourth-youngest president in U.S. history. He was 46 years, 10 months, and 5 days old when he took the oath of office in 1869. Until Roosevelt's ascension to the presidency, Grant had been the youngest president to hold the office. He was inexperienced and his administration plagued by scandal.

Barack Obama Pool / Getty Images News Barack Obama is the fifth-youngest president in U.S. history. He was 47 years, 5 months, and 16 days old when he took the oath in 2009. During the 2008 presidential race, his inexperience was a major issue. He had served only four years in the U.S. Senate before becoming president, but before that had served eight years as a state lawmaker in Illinois. Obama is the youngest living former president.

Grover Cleveland Corbis/VCG via Getty Images / Getty Images Grover Cleveland is the only president who served two non-consecutive terms in office and is the sixth-youngest in history. When he took the oath for the first time in 1885, he was 47 years, 11 months, and 14 days old. The man who many believe to be among America's best presidents was not new to political power. He was previously the Sheriff of Erie County, New York, Mayor of Buffalo, and was then elected Governor of New York in 1883.

Franklin Pierce Franklin Pierce was elected to the presidency at the age of 48 years, 3 months, and 9 days, making him the seventh-youngest president. Montage Images/Getty Images Ten years before the Civil War, Franklin Pierce was elected to the presidency at the age of 48 years, 3 months, and 9 days, making him the seventh-youngest president. His 1853 election would mark four turbulent years with a shadow of what was to come. Pierce made his political mark as a state legislator in New Hampshire, then moved on to the U.S. House of Representatives and the Senate. Pro-slavery and a supporter of the Kansas-Nebraska Act, he was not the most popular president in history.

James Garfield President James Garfield was one of the youngest presidents. Brady-Handy/Epics/Getty Images In 1881, James Garfield took office and became the eighth-youngest president. On the day of his inauguration, he was 49 years, 3 months, and 13 days old. Prior to his presidency, Garfield had served 17 years in the U.S. House of Representatives, representing his home state of Ohio. In 1880, he was elected to the Senate, but his presidential win meant he would never serve in that role. Garfield was shot in July of 1881 and died in September of blood poisoning. He was not, however, the president with the shortest term. That title goes to William Henry Harrison who died one month after his 1841 inauguration.