Yellowstone National Park Visitor Guide - Wyoming & Beyond

Yellowstone National Park occupies 2,219,791 acres across northwestern Wyoming with portions extending into Montana and Idaho. Established by an Act of Congress signed by President Ulysses S. Grant on March 1, 1872, it became the world's first national park, preceding all other protected wilderness designations globally. The park sits atop the Yellowstone Caldera, the largest supervolcano on the North American continent, measuring approximately 30 by 45 miles. The caldera formed during the last supereruption 631,000 years ago, which ejected more than 240 cubic miles of material. The current volcanic system produces the park's 10,000 hydrothermal features, accounting for more than half of the world's active geysers. Old Faithful erupts on average every 92 minutes, with intervals ranging from 60 to 110 minutes, each eruption expelling 3,700 to 8,400 gallons of boiling water to heights between 106 and 185 feet. Steamboat Geyser in the Norris Geyser Basin holds the record as the world's tallest active geyser, with major eruptions reaching over 300 feet, though intervals between major eruptions are unpredictable and have ranged from four days to fifty years.

The Grand Prismatic Spring measures 370 feet in diameter and exceeds 160 feet in depth, making it the largest hot spring in the United States and third largest in the world. Water temperature at the center reaches approximately 189 degrees Fahrenheit. The spring's vivid coloration results from thermophilic bacteria and microbial mats growing in the mineral-rich water, with different heat-tolerant organisms dominating at different temperatures radiating outward from the sterile blue center. The spring discharges an estimated 560 gallons of water per minute. Mammoth Hot Springs on the park's northern edge consists of approximately 50 hot springs flowing over travertine terraces, depositing more than two tons of calcium carbonate daily. The terraces grow and change shape continuously as mineral-laden water from underground travels through limestone, dissolving calcium carbonate and redepositing it at the surface at rates sometimes visible within days.

Yellowstone Lake covers 136 square miles at an elevation of 7,733 feet above sea level, making it the largest high-elevation lake in North America above 7,000 feet. The lake reaches maximum depths of 430 feet and averages 139 feet. Surface water temperatures rarely exceed 60 degrees Fahrenheit even in summer, and the lake remains partially frozen from late December through late May. Underwater thermal features discovered in the 1990s include hydrothermal vents on the lake floor forming spires up to 20 feet tall. The Yellowstone River exits the lake and flows north through the Grand Canyon of the Yellowstone, a gorge carved through volcanic rock measuring approximately 20 miles long and ranging from 800 to 1,200 feet deep. Lower Falls drops 308 feet, nearly twice the height of Niagara Falls, with an average flow of 63,500 gallons per second during peak runoff. Upper Falls upstream drops 109 feet. The canyon walls display yellow, orange, and red coloration from iron compounds in rhyolite rock altered by hydrothermal activity, the source of the Yellowstone name attributed to translations of terms used by the Minnetaree people.

The park supports 67 mammal species. Approximately 5,000 bison constitute the largest wild population on public land in the United States, descended from the 23 individuals that survived poaching in the park during the early 1900s when the continent-wide population fell below 1,000 from an estimated pre-contact population of 30 to 60 million. Gray wolves were extirpated from the park by 1926 following predator control campaigns. Between 1995 and 1997, 41 wolves captured in Canada were reintroduced to Yellowstone under the Northern Rocky Mountain Wolf Recovery Plan. As of December 2023, at least 108 wolves in 11 packs inhabited the park, with several packs ranging partially outside park boundaries. Wolf reintroduction initiated a trophic cascade documented in multiple ecological studies: elk populations declined from pre-wolf counts exceeding 19,000 to fluctuating between 4,000 and 6,000, reducing browsing pressure on aspen and willow, which increased in height and density in riparian zones, stabilizing stream banks and altering channel morphology. Beaver populations increased from one colony in 1996 to twelve colonies by 2009 as willow habitat recovered. Grizzly bear populations within the Greater Yellowstone Ecosystem, which includes the park and surrounding national forests totaling approximately 20 million acres, numbered an estimated 150 individuals in 1975 when listed as threatened under the Endangered Species Act. Population estimates as of 2021 ranged from 728 to over 1,000 bears, leading to delisting in 2017, relisting in 2018 following litigation, and ongoing management debates.

Elk number between 10,000 and 20,000 depending on season and survey methodology, with the Northern Range herd historically the most studied ungulate population in North America. Moose inhabit marshy areas and willow flats with populations estimated between 200 and 400 individuals, significantly below historical abundance attributed to multiple factors including habitat changes, predation, parasites, and vehicle collisions. Pronghorn populations fluctuate between 200 and 500 animals. Bighorn sheep number approximately 300 individuals. Mountain goats, not native to the park, were introduced to Montana in the 1940s and 1950s and have migrated into northern sections of Yellowstone, with the National Park Service implementing removal operations beginning in 2018 to protect native species and fragile alpine habitats. Coyote populations declined following wolf reintroduction as wolves killed coyotes and appropriated their kills, with coyote numbers dropping by approximately 50 percent in wolf-occupied areas.

The park contains more than 290 waterfalls exceeding 15 feet in height, though many remain unnamed and accessible only by off-trail hiking. Yellowstone hosts 16 fish species, five native and 11 introduced through stocking programs that ended in 1955. Native cutthroat trout populations in Yellowstone Lake declined dramatically following illegal introduction of non-native lake trout first discovered in 1994. Lake trout consume cutthroat trout and spawn in deep water inaccessible to bears and birds that historically relied on cutthroat spawning runs in tributaries. The National Park Service has removed more than 4 million lake trout through gillnetting since 1996, an ongoing suppression effort costing over $2 million annually. Native Arctic grayling persist only in a few remote streams. Mountain whitefish remain present throughout suitable waters. New Zealand mud snails, first detected in Yellowstone in 1994, have colonized waters throughout the park, reaching densities exceeding 500,000 individuals per square meter in some locations, outcompeting native invertebrates that serve as food for fish and birds.

Approximately 4.5 million people visited Yellowstone in 2023. Visitor numbers have increased from approximately 2 million in the 1970s, creating congestion concentrated in the summer months of June through August, when 70 percent of annual visitation occurs. The park's five entrances include the North Entrance at Gardiner, Montana, the only entrance accessible by road year-round, and the Northeast Entrance at Cooke City, Montana, which closes from mid-October through late May depending on snow. The West Entrance at West Yellowstone, Montana, the South Entrance near Grand Teton National Park, and the East Entrance near Cody, Wyoming, typically open in mid-April or early May and close in early November. During winter, West Yellowstone serves as the primary access point for oversnow vehicles. The Grand Loop Road forms a figure-eight totaling 142 miles, connecting the park's major features with a posted speed limit of 45 miles per hour on most sections, reduced to 25 miles per hour near thermal areas and where wildlife congregates. Reconstruction and rehabilitation of road segments occurs annually due to frost heave, thermal ground movement, and heavy use, with major rehabilitation projects requiring partial closures outside peak season.

Nine visitor centers and museums provide interpretation and educational exhibits. The Old Faithful Visitor Education Center, which opened in 2010 after replacing a 1970s structure, receives over 3 million visits annually and features exhibits on hydrothermal geology and predictive data for geyser eruptions. The Albright Visitor Center at Mammoth Hot Springs occupies the former bachelor officers' quarters built in 1909 when the U.S. Army administered the park from 1886 to 1918. Twelve campgrounds within the park provide 2,000 campsites total, with five operated by the National Park Service on a first-come basis and seven operated by concessionaire Xanterra Parks and Resorts accepting reservations. Madison Campground contains 278 sites. Bridge Bay Campground offers 432 sites, the largest in the park. Fishing Bridge RV Park accommodates only hard-sided camping vehicles due to bear activity, with no tents permitted. The park contains nine lodges and hotels totaling approximately 2,200 rooms. Old Faithful Inn, designed by architect Robert Reamer and opened in 1904, stands as the largest log structure in the world, with the main lodge constructed using lodgepole pine harvested from the park. The lobby soars seven stories beneath a gabled roof, centered on a volcanic rhyolite fireplace rising 85 feet.

Over 1,000 miles of trails traverse the park, ranging from boardwalk loops under one mile around major thermal features to backcountry routes exceeding 20 miles. Approximately 300 designated backcountry campsites require advance permits obtained through a reservation system opening in mid-March or in-person permits issued 48 hours before planned entry. Backcountry campsites in areas frequented by bears require food storage in bear-resistant containers or hanging from provided poles. The park issues approximately 35,000 backcountry camping permits annually. The Continental Divide Trail, a 3,100-mile route from Mexico to Canada, passes through Yellowstone for approximately 65 miles. Horse use requires certification that animals have not consumed hay potentially carrying invasive plant seeds for 120 hours before entry. The park maintains approximately 50 miles of trails designated for stock use with 49 designated backcountry stock campsites.

Yellowstone sits at elevations ranging from 5,282 feet at the North Entrance to 11,358 feet at Eagle Peak in the Absaroka Range along the park's eastern boundary. The park experiences a subarctic climate with long cold winters and short cool summers. Average overnight lows in January at Mammoth Hot Springs fall to 9 degrees Fahrenheit, with average highs reaching only 30 degrees. At Old Faithful, average January lows drop to -4 degrees Fahrenheit. Snowfall at higher elevations exceeds 200 inches annually, while the northern range near Gardiner receives approximately 60 inches. Summer afternoon temperatures typically reach the mid-70s to low 80s Fahrenheit at lower elevations, though freezing temperatures and snowfall can occur in any month. The park recorded its lowest temperature of -66 degrees Fahrenheit at Riverside Station on February 9, 1933. Lightning strikes cause approximately 24 wildfires annually on average. The fires of 1988 burned approximately 793,000 acres, roughly 36 percent of the park, during a severe drought year when precipitation from January through July totaled 6.23 inches compared to the average of 11 inches. The fires attracted national media attention and policy debates about wildfire suppression, ultimately reinforcing the park's policy allowing natural fires to burn under appropriate conditions while suppressing human-caused fires.

The park employs approximately 750 permanent and seasonal National Park Service staff. Law enforcement rangers enforce federal regulations within park boundaries, with jurisdiction concurrent with state and county authorities. The park averages approximately 300 search and rescue operations annually. Emergency medical services transport serious cases by helicopter to hospitals in Bozeman, Montana, Idaho Falls, Idaho, or Billings, Montana, with ground transport times exceeding two hours from central locations. The park operates holding cells for temporary detention but transfers arrestees requiring extended incarceration to county facilities outside the park. Between 1870 and 2022, at least 350 deaths occurred in the park, with thermal features accounting for at least 22 confirmed fatalities. On June 7, 2016, a visitor died after leaving the boardwalk at Norris Geyser Basin and slipping into a hot spring with water temperature near boiling; the body dissolved completely in the acidic water. Bison injure several visitors each year, with at least 56 documented injuries from bison between 2000 and 2015. Park regulations require maintaining at least 25 yards from bison and elk and at least 100 yards from bears and wolves. Bear-caused human fatalities in the park total eight documented cases from 1872 to 2022, with five deaths attributed to grizzly bears and three to black bears. The most recent fatal bear attack occurred in 2015 when a grizzly killed a hiker on the Elephant Back Loop Trail near Yellowstone Lake.

Entrance fees as of 2024 are $35 per private vehicle, $30 per motorcycle, and $20 per individual entering by foot or bicycle, valid for seven consecutive days and covering both Yellowstone and Grand Teton National Parks. The America the Beautiful Annual Pass costs $80 and grants entrance to all National Park Service sites, U.S. Forest Service sites, and other participating federal lands for one year. Cell phone service exists only in limited areas near developed locations including Mammoth, Old Faithful, and Canyon Village, with most of the park lacking coverage from any carrier. Fuel stations operate at seven locations within the park during summer season, with only Mammoth and Old Faithful Inn remaining open in winter. Gasoline prices typically exceed regional averages by 50 cents to one dollar per gallon due to transport costs and limited competition. The park's concessionaire operates general stores at major developed areas selling groceries, camping supplies, and souvenirs. Limited medical services operate at three urgent care clinics in summer at Mammoth, Old Faithful, and Lake Village, staffed by physician assistants and emergency medical technicians. No full hospital facilities exist within park boundaries.

Winter access from mid-December through mid-March requires snowcoaches or snowmobiles, with daily limits capping snowmobile entry at 110 commercially guided groups per day and prohibiting private snowmobile use except for two short access roads. Snowcoaches, typically tracked vehicles or vans modified with tracks, transport passengers from West Yellowstone or Mammoth to Old Faithful and Canyon, with round-trip tours costing between $250 and $400 per person. The park grooms approximately 300 miles of roads for oversnow vehicle use. Cross-country skiing and snowshoeing on ungroomed terrain remain unrestricted in most areas. The Upper Geyser Basin trail system, accessible from Old Faithful, receives regular grooming for skier use. Oversnow visitor numbers from December through March total approximately 45,000 annually, less than 2 percent of summer monthly visitation.

Yellowstone's thermal features require strict adherence to boardwalks and designated trails due to unstable ground and water temperatures exceeding 200 degrees Fahrenheit. Thermal areas contain thin crusts overlying boiling or near-boiling water and mud, with ground that can collapse under weight. Water acidity in some features approaches that of battery acid, with pH values below 2 recorded at Norris Geyser Basin. Entering thermal features or collecting thermal water, rocks, or organisms violates federal law and carries penalties including fines up to $5,000 and six months imprisonment. Thermal monitoring systems detected a notable increase in ground uplift at the Norris Geyser Basin beginning in 2013, with ground rising approximately three inches annually before stabilizing in 2014, attributed to pressurized water migrating through subsurface fractures. The United States Geological Survey operates the Yellowstone Volcano Observatory, maintaining continuous monitoring through seismometers, GPS stations measuring ground deformation, and stream gauges measuring water discharge. The region experiences between 1,500 and 2,500 earthquakes annually, most too small to feel, with magnitudes below 3 accounting for the vast majority. The largest recorded earthquake in the park occurred on August 17, 1959, registering magnitude 7.3 with an epicenter just outside the park's northwestern boundary near Hebgen Lake, Montana, killing 28 people, most at a campground buried by a landslide triggered by the quake.