Before Herbert Hoover we have no record of left-handed presidents. Shockingly, it’s because before Hoover, being left-handed was considered a disability. Teachers would actually suppress students from using their left-hand dominantly. So, it wasn’t until the 20th century that handedness was determined in presidents or recorded about them.
Herbert Hoover was the first president to be said to be left-handed. Harry Truman, Gerald Ford, George H.W. Bush, Bill Clinton, and Barack Obama are all lefties. Now, 6 out of the last 14 presidents is a lot considering only 10 percent of our general population is left-handed. Ronald Reagan was the ambidextrous president. James Garfield was said to be able to write Latin with his right hand while simultaneously writing in Greek with his left hand.
Reagan was supposedly dominantly a left-handed person, but forced to write with his right hand by his teachers. In all his photos, he is seen signing with his right hand, though. So, that is why it is said that he is ambidextrous. The same is said to be true about Harry S. Truman.