No one is entirely sure how many left-handed presidents the US has had, since there aren't really clear records before 1929. Of those presidents whose handedness is known, six were left-handed, including Barack Obama, Bill Clinton, and Harry Truman. Ronald Reagan was said to be ambidextrous, so if he is counted then half of the US presidents since 1929 have been left-handed.

Former President Harry Truman, who was left-handed.

In chronological order, the known left-handed presidents are: Herbert Hoover, Harry Truman, Gerald Ford, George H.W. Bush, Bill Clinton, and Barack Obama. Other presidents who may have been ambidextrous or left-handed include Ronald Reagan, James Garfield, and Thomas Jefferson. If Reagan is counted as left-handed, then the United States was controlled by a left-handed president for 20 years from 1981 to 2001, which is unusual considering how rare left-handed people are in the general population.

Thomas Jefferson, who was ambidextrous.

There are some disputes about the list of left-handed presidents. Prior to the 20th century, left-handedness was regarded as a negative character trait, and it is possible that more presidents prior to the 20th century were left-handed, but they concealed that fact. “Retraining” of left-handed individuals was also very common well through the 20th century, with young children being forced to write with their right hands, even if their left hands were dominant.

President James Garfield may have been either left-handed or ambidextrous.

Two of the presidents who could write with their left hands, Garfield and Reagan, experienced assassination attempts. Garfield probably would have survived if not for a series of mistakes on the part of his doctors, but he died after weeks of infection and misery. Reagan survived, as the bullet barely missed his heart. Truman and Ford were both vice presidents who succeeded to the office of the residency, after the death of President Roosevelt in 1945 and the resignation of President Nixon in 1974. Ford was the only president who never won a national election, as he was appointed to the office of the Vice-Presidency after Nixon's original running mate, Spiro Agnew, resigned from the office in disgrace after it came out that he took almost $30,000 US Dollars (USD) in bribes.

Herbert Hoover was the first known left-handed president.

Given that an estimated seven to 10 percent of the population is left-handed, six out of 14 presidents since 1929 being left-handed is a pretty remarkable statistic, and a cause for pride among some members of the left-handed community. Left-handed individuals are supposedly more creative and articulate than their right-handed counterparts, due to differences in brain function, which may have something to do with the high number of left-handed presidents.

Prior to the 20th century, left-handedness was considered a negative character trait.

Ronald Reagan was said to be ambidextrous.