Calcite Springs Overlook and Yellowstone River, Yellowstone National Park, Wyoming (© Rebecca L. Latson/Getty Images)

Today, the National Park Service celebrates another trip around the sun—and nearly 85 million acres of American beauty under its care. From geysers that spout like soda cans to ancient cliff dwellings tucked into canyon walls, the NPS has spent over a century preserving, protecting, and inviting people to take a hike—literally. In 1916, President Woodrow Wilson signed the Organic Act into law, officially creating the NPS to 'conserve the scenery and the natural and historic objects.' Since then, the NPS has grown to oversee more than 400 sites, including national parks, battlefields, monuments, and seashores.