<human>:  What is the historical significance of May 4th?
<bot>: May 4th has a great historical significance in the United States as it marks the anniversary of what has come to be known as the Kent State Massacre. On May 4, 1970, members of the Ohio National Guard opened fire on students bearing non-lethal weapons, at a protest against the Vietnam War at Kent State University. Four students were killed and nine were injured, the event became a symbol of the anti-war movement.