YELLOWSTONE NATIONAL PARK, WYOMING - MAY 17: Visitors gather at an overlook at the Grand Canyon of the Yellowstone on May 17, 2026 in Yellowstone National Park, Wyoming. Yellowstone National Park became the nation’s first national park on March 1, 1872, when President Ulysses S. Grant signed a congressional act protecting the land “for the benefit and enjoyment of the people.” Today, the 2.2-million-acre park thrives as part of one of Earth's last nearly intact large temperate ecosystems, famously preserving over 10,000 hydrothermal features and around 500 geysers—roughly 50 percent of the world’s total. Boasting the largest concentration of mammals in the lower 48 states, Yellowstone stands as the only place in the U.S. where bison have roamed continuously since prehistoric times. Native American communities inhabited and conserved the lands for over 10,000 years, with 27 individual tribes recognized by the National Park Service as carrying modern-day and historic ties to Yellowstone. National Park Week will celebrate America’s 250th anniversary with a weeklong celebration in August featuring hundreds of commemorative events at many of America’s 433 national parks under the theme “Celebrate America’s Story”. (Photo by Mario Tama/Getty Images)