Yellowstone National Park

Yellowstone was signed into existence on March 1, 1872 as the world's first national park, and over 150 years later it still holds roughly half of the planet's known geothermal features — geysers, hot springs, mudpots and travertine terraces concentrated above one of Earth's largest active volcanic systems. The park sprawls across 2.2 million acres in the northwest corner of Wyoming and into Montana and Idaho, with five entrances feeding a 142-mile figure-eight Grand Loop that links the Upper Geyser Basin, Mammoth Hot Springs, the Lamar Valley wildlife corridor, and the Grand Canyon of the Yellowstone. For freight traffic moving on I-90, the practical gateway is Livingston, Montana — Exit 333 — with US-89 dropping south into Paradise Valley to reach the only entrance that stays open year-round.

• First national park in the world (March 1, 1872)
• Holds about 50% of the planet's known geysers and over 10,000 hydrothermal features
• Sits atop a 30-mile-wide active volcanic caldera
• Largest concentration of free-roaming wildlife in the lower 48 (bison, elk, wolves, grizzlies)
• Five entrances; only the North Entrance (Gardiner) road stays open to wheeled vehicles year-round

• Old Faithful
• Grand Prismatic Spring
• Mammoth Hot Springs travertine terraces
• Lamar Valley wildlife corridor
• Grand Canyon of the Yellowstone (Lower Falls)

Best months: Late May through September — full Grand Loop access, all visitor centers open, predictable weather.

Closures: Most internal park roads close to wheeled vehicles from early November through mid-April. Only the road from Gardiner through Mammoth to Cooke City stays plowed all winter. Snowcoach and snowmobile access (with permits) is the only way into the interior November through March.

Notes: Spring road plowing is unpredictable — Beartooth Pass on the Northeast Entrance road can stay closed into late May.