Yellowstone & Grand Tetons

Yellowstone's geyser basins hold over 10,000 hydrothermal features and about 500 geysers — roughly half the world's total. Old Faithful erupts every 44 to 125 minutes, and Grand Prismatic Spring, about 370 feet across, is the largest hot spring in the U.S. The Grand Canyon of the Yellowstone drops over the 308-ft Lower Falls.

Wildlife watching in the Lamar and Hayden valleys, paddling Jenny and Jackson lakes in Grand Teton, fly-fishing the Snake and Madison, and winter snowcoach tours fill the calendar.

Summer (June–August) opens all roads and trails but brings the heaviest crowds and full parking lots by 9 a.m. at marquee sites. September and early October bring the elk rut, golden aspens, and thinner crowds.

From roughly early November to mid-April most interior roads close to cars; the park becomes a snowbound world accessible by snowcoach and snowmobile, with geysers steaming against the snow and wildlife concentrated in the valleys.

This is the core of the Greater Yellowstone Ecosystem, one of the last nearly intact temperate ecosystems on Earth. Gray wolves, famously reintroduced in 1995, share the range with grizzly and black bears, around 4,000–5,000 bison (the largest wild herd in the U.S.), elk, moose, pronghorn, and bighorn sheep.

The Lamar Valley, dubbed 'America's Serengeti,' offers the densest wildlife viewing; trumpeter swans and bald eagles patrol the rivers.

The 22-million-acre Greater Yellowstone Ecosystem spans forest, sagebrush, alpine, and geothermal habitats. The 1995 wolf reintroduction restored a top predator and reshaped elk behavior, riverbanks, and beaver populations — a landmark case study in trophic cascades.

Fire is a natural force here; the 1988 fires burned about 36% of the park and renewed its lodgepole pine forests.

Yellowstone sits atop one of Earth's largest volcanic systems; its magma reservoir powers the hydrothermal features, and the last of three caldera-forming super-eruptions occurred about 640,000 years ago. The geyser basins host heat-loving microbes that paint the springs and advanced the science of life in extreme environments.

The Tetons, by contrast, are young fault-block mountains rising along the Teton Fault with no foothills — 13,775-ft Grand Teton looms about 7,000 feet above the valley floor.

At least 27 tribes — including the Eastern Shoshone, Crow, Blackfeet, and the Tukudika (Sheep Eater) Shoshone who lived year-round in the high country — have deep ties to this land. Yellowstone became the world's first national park on March 1, 1872.

Grand Teton was established in 1929 and expanded in 1950 with land quietly bought and donated by John D. Rockefeller Jr., who also funded the parkway linking the two parks.

Twenty-seven associated tribes are reconnecting with Yellowstone through expanded interpretation. The town of Jackson, with its elk-antler arches and Western galleries, anchors a cowboy-meets-resort culture.

Near the Tetons, the National Museum of Wildlife Art and the winter sleigh rides through the National Elk Refuge (which winters thousands of elk) are highlights.

A UNESCO World Heritage Site, Yellowstone is a global model and proving ground for ecosystem-scale conservation, including the wolf reintroduction. Bison brucellosis disputes with Montana ranchers, grizzly recovery and delisting debates, and managing over 4 million annual visitors define the work.

Jackson Hole Airport (JAC) sits inside Grand Teton; Bozeman (BZN), Cody, and Idaho Falls also serve the region, linked by the Rockefeller Parkway. Yellowstone is vast — over 250 miles of road loop the park, so allow long drive times.

Most interior roads close to wheeled vehicles from early November to mid-April; an entrance pass is required.

Thermal areas are lethal — the ground is thin crust over near-boiling, acidic water, and people have died leaving the boardwalks. Keep 100 yards from bears and wolves and 25 yards from bison and elk; bison injure more visitors than any other animal. Carry bear spray, store food properly, and prepare for cold nights and snow any month.

An entrance pass is required; stay on boardwalks in thermal areas and at legal wildlife distances. Drones are banned, and backcountry trips require permits.

Bear spray is strongly advised, food storage is mandatory, and throwing objects into geysers or hot springs is illegal and damaging.

Visit thermal basins and wildlife valleys at dawn for the best light, fewest crowds, and most active animals. Always carry and know how to use bear spray. Reserve in-park lodging up to a year ahead, bring a spotting scope for the Lamar and Hayden valleys, and never step off the boardwalks.

Grand Teton adjoins Yellowstone to the south, with Jackson Hole's resort town and ski area. Cody, Wyoming (Buffalo Bill country) lies east, and the Beartooth Highway climbs to nearly 11,000 feet from the northeast. Idaho's Henrys Fork and the Wind River Range extend the wild country.