On March 28, 1979, a partial nuclear meltdown occurred at the Three Mile Island power plant near Harrisburg, Pennsylvania. This incident, the most serious accident in U.S. commercial nuclear power plant history, was caused by a combination of equipment failures, design-related problems, and human errors. Luckily, it didn't lead to any immediate deaths or injuries, but it sparked widespread fear, controversy, and changes in regulations and operational procedures for nuclear power plants.