Yellowstone National Park is a 2.2‑million‑acre protected area in the western United States administered by the National Park Service. Established by the Act of March 1, 1872, it is widely regarded as the world’s first national park; the act set aside the Yellowstone region as a “public park or pleasuring‑ground for the benefit and enjoyment of the people,” creating a new federal model for landscape conservation. According to the National Archives, the statute was signed by President Ulysses S. Grant, following the 1871 Hayden Survey’s influential advocacy. While Yellowstone is generally considered the first national park globally, Britannica notes scholarly debate referencing earlier protections such as Mongolia’s Bogd Khan Mountain. National Archives;
Britannica. (
archives.gov)
Geography and designation
- –Location: The park lies mostly in Wyoming with portions in Montana and Idaho; summary figures commonly cited are about 3,472 square miles (8,991 km²), or roughly 2,221,766 acres, with approximately 96% of the park in Wyoming, 3% in Montana, and 1% in Idaho.
Yellowstone Forever. (
- –International recognition: Yellowstone was designated a UNESCO Biosphere Reserve in 1976 and inscribed as a World Heritage Site in 1978 (criteria vii–x). UNESCO lists the property at 898,349 ha and records its 1995–2003 placement on the Danger List.
UNESCO MAB;
UNESCO World Heritage Centre;
NPS World Heritage page. (
Geology and the Yellowstone Caldera
- –Volcanic history: The Yellowstone Plateau volcanic field experienced three major explosive events at ~2.1 Ma (Huckleberry Ridge Tuff), ~1.3 Ma (Mesa Falls Tuff), and ~640 ka (Lava Creek Tuff), the last forming a 45×85 km caldera. Subsequent rhyolitic lavas erupted between ~180 ka and 70 ka; the most recent lava is ~70–77 ka.
USGS Yellowstone Volcano Observatory. (
- –Hydrothermal system: Yellowstone hosts more than 10,000 hydrothermal features and the world’s largest concentration of active geysers (over 500).
- –Tallest active geyser: Steamboat Geyser in Norris Geyser Basin is recognized as the world’s tallest active geyser; USGS and NPS document major eruptions exceeding 300 ft (≈90 m) and an active phase beginning in 2018 with many recorded eruptions.
- –Notable features: Old Faithful erupts on average about every 90 minutes (range roughly 50–127 minutes), lasting 1.5–5 minutes and reaching 106–184 ft, as documented by the NPS and USGS.
Britannica overview;
Hydrology and landforms
- –Yellowstone Lake, at 7,733 ft (2,357 m), is the largest high‑elevation lake in North America; NPS provides dimensions of roughly 20×14 miles and about 132–136 square miles of surface area.
Ecology and wildlife
- –Yellowstone protects the largest concentration of mammals in the contiguous United States, with 67 mammal species documented. NPS quick facts note seven native ungulates and seven large predators, including grizzly bear, black bear, and Gray wolf. As of 2024–2025, NPS reports about 1,030 grizzly bears in the Greater Yellowstone Ecosystem, approximately 5,400 American bison as of August 2024, and at least 108 wolves living primarily in the park as of January 2025.
- –Wolf restoration: Wolves were reintroduced to Yellowstone in 1995–1996 under a federal recovery program; NPS summarizes 41 wolves released in Yellowstone and 35 in central Idaho, with continued monitoring thereafter. Recent peer‑reviewed research (Forest Ecology and Management, 2025) reports significant aspen recovery on the park’s northern range linked to the return of large carnivores; mainstream coverage summarizes these findings.
Washington Post. See also: journal://Forest Ecology and Management|Changing aspen stand structure following large carnivore restoration in Yellowstone|2025. (
Indigenous histories and contemporary partnerships
- –Yellowstone is the traditional homeland of many Tribal Nations. The NPS recognizes 27 Associated Tribes with ancestral and modern connections to the area, and the Yellowstone Tribal Heritage Center—opened in 2022 in the Old Faithful area—hosts Indigenous artists and knowledge‑holders each season.
Historical administration and protection
- –After establishment, management challenges prompted the U.S. Army to administer the park from 1886 to 1918 from Fort Yellowstone at Mammoth Hot Springs, developing protection practices later adopted by the NPS (created 1916). NPS histories recount the 1894 National Park Protection Act (often called the Lacey Act) after the high‑profile arrest of a bison poacher, providing the legal tools to prosecute crimes in the park.
NPS “Birth of a National Park”. (
- –Fire history: In 1988, approximately 793,880 acres burned inside the park (~36%), part of ~1.2–1.4 million acres across the Greater Yellowstone Ecosystem; NPS overviews document “Black Saturday” (Aug. 20) and subsequent policy evolution.
Hydrologic hazards and infrastructure resilience
- –In June 2022, extreme rainfall and snowmelt produced a 500‑year flood that destroyed segments of the North Entrance Road and parts of the Northeast Entrance Road. The park rapidly opened a temporary route (Old Gardiner Road) and continues multi‑year planning for a resilient permanent alignment and related bridge projects.
NPS PEPC—North Entrance Road;
Visitation and management
- –Visitation is highly seasonal. Yellowstone hosted 4,501,382 recreation visits in 2023 (second‑busiest year on record after 2021) and year‑to‑date visitation through August 2025 totaled 3,547,967. Monthly NPS updates provide recent figures and context for the post‑flood rebound.
- –Current leadership: Superintendent Cam Sholly has served since October 2018, leading recovery from the 2022 flood and expanding Tribal engagement initiatives.
Notable places
- –Hydrothermal basins and iconic sites include Old Faithful, Grand Prismatic Spring, Mammoth Hot Springs, Norris Geyser Basin, and West Thumb Geyser Basin. NPS and USGS provide interpretive and scientific context for visitor areas across the Grand Loop Road.
Selected reference works
- –The park’s geysers and springs are extensively cataloged in T. Scott Bryan’s reference work. [The Geysers of Yellowstone](book://T. Scott Bryan|The Geysers of Yellowstone|University Press of Colorado|2008).