This day is the anniversary of the 2018 March for Our Lives, when over a million people protest in cities across the U.S., calling for legislative action to address gun violence, following a mass shooting that had claimed the lives of 17 students at Stoneman Douglas High School in Parkland, Florida, the previous month. Organized by survivors, with highly visible celebrity support and participation, the primary event in D.C. features only speakers who are high school age or younger.

With a large, well-coordinated social media component, the event becomes a lightning rod for partisan politics online and in the news media.

Four years later, the Bipartisan Safer Communities Act is signed into law, including gun safety measures and funding for schools for safety and mental health programs.