Yellowstone National Park

Yellowstone: A Supervolcano With Geysers and Very Assertive Bison

Yellowstone was established as a national park in 1872, the first in the world. It sits mostly in Wyoming, with edges in Montana and Idaho, and covers 9,000 square kilometres of active geothermal landscape sitting above one of the largest volcanic hotspots on earth. The last major eruption was 640,000 years ago. The geothermal features exist because the crust here is thin and the magma is relatively close to the surface. That geological context is worth holding in mind as you stand next to a mud pot or watch a geyser; this is not just scenery, it is a functioning piece of the planet’s heat exchange system.

Fee note for 2026: Starting January 1, 2026, international visitors (non-US residents, including Canadians) pay an additional USD 100 per person on top of the standard USD 35 per-vehicle entry fee. The standard America the Beautiful annual pass for non-residents increased to USD 250.

The Main Geothermal Areas

Old Faithful erupts approximately every 91 minutes; the interval varies between 65 and 125 minutes, and the visitor centre posts the predicted next eruption time. The eruption lasts around 3.5 minutes and shoots water 32 to 56 metres high. Arrive 10 minutes before the predicted time; the boardwalk benches fill quickly.

The Upper Geyser Basin around Old Faithful is the most concentrated geyser field in the world: 150 geothermal features within 4 square kilometres. The Castle, Beehive, and Grand Geysers all have irregular eruption schedules that the ranger station predicts; ask when you arrive. Beehive erupts once or twice a day and is the more dramatic of the three.

Grand Prismatic Spring in the Midway Geyser Basin is the one that fills travel photographs with rings of orange, yellow, and green. The colours come from heat-adapted bacteria growing in progressively cooler water toward the edges. The 2017 overlook trail on the hill above the basin gives the aerial view that context requires; it costs around USD 3 on top of park admission and is worth every cent.

Mammoth Hot Springs in the north is a series of terraced travertine deposits – white, orange, and pale yellow – built up over millennia as hot water dissolves calcium carbonate and deposits it on the surface. The terraces shift their shape seasonally.

Norris Geyser Basin is the hottest and most geologically active basin in the park, with the highest ground temperatures recorded anywhere at Yellowstone. Steamboat Geyser here is the world’s tallest active geyser at 90 to 120 metres; its eruption schedule is irregular, alternating between dormant years and active periods.

Wildlife

The Lamar Valley in the northeast corner is where wolves are most reliably seen. The Yellowstone Wolf Project reintroduced grey wolves in 1995 and the current population runs around 100 animals in eight to ten packs. The best viewing is at dawn and dusk from road pullouts along the Lamar Valley road. The Yellowstone Forever Institute runs wolf-watching courses from the Lamar Buffalo Ranch with naturalist guides who track specific packs – worth booking if you have more than a day in the area.

Bison are everywhere and are not tame. They injure more visitors each year than any other animal in the park. The minimum safe distance is 25 yards (23 metres). Bull bison in rut, late July through August, are especially unpredictable.

Grand Canyon of the Yellowstone

The Yellowstone River has carved a 350-metre canyon through rhyolite bedrock. Artists Point on the South Rim gives the most reproduced view in the park – looking along the canyon to the 94-metre Lower Falls. Worth the short walk.

Where to Stay

Old Faithful Inn is the architectural landmark of the park: a massive log structure built in 1904 with the largest log lobby in the world. Rooms book out 13 months in advance when reservations open at Xanterra.com. If you cannot get the Inn, the adjacent Old Faithful Snow Lodge is the next best option.

Lake Yellowstone Hotel on the north shore is the more sedate option, a Colonial Revival building from 1891 with lake views.

For camping, most sites are reservable at recreation.gov. Slough Creek campground in the Lamar Valley is the wolf-watching option. Bridge Bay is the largest and most reliably bookable.

When to Go

September and early October offer cooler temperatures, dramatically fewer visitors than July and August, and excellent wildlife activity before winter. The difference in crowd density between July and September is substantial; if you have any flexibility, choose September.

Winter (December through February) is a different park: roads closed to cars but open to snowcoaches, geothermal features more dramatic against snow, fewer than 3,000 visitors per day versus 25,000 in July. Extraordinary if you are prepared for it.