1. On June 21, 1788, South Carolina became the eighth state to ratify the United States Constitution. The state's ratification was a significant moment in the formation of the federal government and established South Carolina's place in American history.

2. In 1864, General William T. Sherman's Union Army arrived in the city of Charleston, beginning a siege that would last until February 1865. The siege and subsequent destruction of the city marked a significant turning point in the Civil War and had long-lasting effects on South Carolina, particularly in the city of Charleston.

3. June 21, 1944 saw the launch of Operation Neptune, the naval component of the D-Day invasion that occurred in World War II. While South Carolina was not directly involved in the invasion, the state's ports were used as a staging ground for troops and supplies heading to Europe.

4. On June 21, 1964, civil rights activist James Chaney was murdered, along with two other activists, in Neshoba County, Mississippi. Chaney was a native of Meridian, Mississippi, but had ties to South Carolina, having attended a training program at a college in the state just prior to his death. The case became a national outrage and highlighted the ongoing struggle for civil rights in the United States.

5. In 2015, a mass shooting occurred at the Emanuel African Methodist Episcopal Church in Charleston on June 17, which falls just four days before June 21. The shooting, carried out by a white supremacist, claimed the lives of nine people and sparked a national conversation about racism, gun violence, and the history of the Confederate flag. While not directly related to June 21, the shooting is a significant event in recent South Carolina history and has had a lasting impact on the state and the country as a whole.