The U.S. National Park Service (NPS) is a federal agency responsible for managing national parks, monuments, and other conservation and historical properties across the United States. Established in 1916, the NPS aims to preserve the natural and cultural resources of these sites for future generations while providing public enjoyment and education. The agency generates revenue through entrance fees, recreational permits, and partnerships with private entities. Key historical milestones include the establishment of Yellowstone as the first national park in 1872 and the passage of the Organic Act, which formalized the NPS's mission.