1. On April 20, 1861, Georgia seceded from the Union and joined the Confederacy, as tensions between North and South escalated into the American Civil War. Georgia's declaration of secession stated the state's belief in states' rights, including the right to own slaves, and its intention to join with other Southern states to form a new nation.

2. On April 20, 1980, a group of armed men stormed the Iranian embassy in London, taking 26 hostages. The siege lasted for six days, ending with the death of five hostages and all but one of the hostage-takers. One of the hostage-takers, Fowzi Nejad, had Georgia ties; he had studied in Atlanta and later lived in suburban Norcross, where he worked as a waiter before returning to Iran.

3. On April 20, 1999, two students opened fire at Columbine High School in Colorado, killing 13 people and injuring more than 20 others. The shooting is considered one of the deadliest school shootings in U.S. history and prompted a national debate about gun control and school safety.

4. On April 20, 2005, the BP Deepwater Horizon oil rig exploded in the Gulf of Mexico, killing 11 workers and triggering the largest oil spill in U.S. history. The spill, which lasted for 87 days, released an estimated 4.9 million barrels of oil into the Gulf, devastating marine life and the local economy.

5. On April 20, 2018, hundreds of thousands of people gathered in Atlanta and across the country for the March for Our Lives, a student-led protest against gun violence and for stricter gun control laws. The march, which was inspired by the Parkland shooting earlier that year, spawned a movement and renewed activism around gun control issues.