"Missing 411" refers to a series of unexplained disappearances of people, primarily in national parks and wilderness areas in the United States. The term was popularized by former police officer David Paulides, who has documented cases where individuals have vanished under mysterious circumstances, often without a trace. The phenomenon has sparked interest and debate among researchers, outdoor enthusiasts, and the general public. Some theories suggest environmental factors, while others propose more unusual explanations. The cases often share common elements, such as the terrain and the circumstances surrounding the disappearances, leading to ongoing investigations and discussions.