At least how many U.S. presidential assassination attempts or plots are known to have occurred since 1864?

There has been a number of presidential assassination attempts in the history of the US. More than 20 attempts have occurred, with some of them being successful. Most of the historians agree, that the majority of the assassinations was motivated politically. Still, several attackers were mentally unstable and attempted to kill a president for some odd reasons. For example, Richard Lawrence, a painter who attempted to kill Andrew Jackson, was in the end found not guilty as he was insane.

Four sitting American presidents have been assassinated by gunshot. These cases are well-known:

• Abraham Lincoln (the 16th President)
• James A. Garfield (the 20th President)
• William McKinley (the 25th President)
• John F. Kennedy (the 35th President)

Two presidents were injured in attempted assassinations, also by gunshot:

• Theodore Roosevelt (the 26th President)
• Ronald Reagan (the 40th President)

The 44th president of the country, Barack Obama, has been threatened with assassination at least 8 times, which makes him the target of most plots and attempted assassinations. Anyway, every president since JFK has been under the threat of assassination at least once.