Smallpox was once one of the deadliest diseases in human history. Caused by the variola virus, it spread easily and often killed those it infected. Survivors were frequently left with severe scarring. According to the CDC, smallpox killed about 30% of infected people in the 20th century alone. Because of its devastating impact, it became the focus of a massive global vaccination effort.

That effort succeeded. Thanks to widespread vaccination, the World Health Organization declared smallpox eradicated worldwide in 1980. In the United States, routine vaccinations stopped in 1972 after the disease had already been eliminated domestically. The smallpox vaccine was unique.

It was administered using a two-pronged needle that punctured the skin several times, introducing a live but weaker virus called vaccinia. The body’s reaction caused a blister that eventually healed into a permanent scar. Today, that scar is more than a mark—it’s a symbol of one of humanity’s greatest public-health victories. If you have one, you carry a visible piece of history.