On May 18, 2000, the final episode of the popular television series 'The X-Files' aired, concluding the show's nine-season run.

Mount St. Helens erupted on May 18, 1980, in Washington State, resulting in the deadliest volcanic eruption in U.S. history, killing 57 people.

On May 18, 1969, the Apollo 10 mission was launched, which served as a 'dress rehearsal' for the first moon landing, testing all systems except landing.