Yellowstone National Park

Yellowstone National Park, established in 1872 as the first national park in the United States, spans 2.2 million acres across Wyoming, Montana, and Idaho. The park sits atop one of the world's largest volcanic hotspots, powering over 10,000 hydrothermal features — roughly half the planet's total — including geysers, hot springs, fumaroles, and mud pots. Old Faithful, erupting every 44 to 125 minutes to heights of 100 to 185 feet, is the park's flagship attraction and anchors the Upper Geyser Basin, where a dense cluster of active geysers can be explored on boardwalk loops. The nearby Old Faithful Inn, a landmark log-and-timber structure from 1904, makes an excellent base for watching multiple eruptions over a morning or evening. The Grand Prismatic Spring in the Midway Geyser Basin is the park's largest hot spring: at 370 feet in diameter, its vivid rings of orange, yellow, and green microbial mats are best appreciated from the Fairy Falls Trail overlook above the basin. The Grand Canyon of the Yellowstone, a vivid yellow-walled gorge cut by the Yellowstone River, features two major waterfalls — the 308-foot Lower Falls and the 109-foot Upper Falls — visible from easily reached overlooks on the North and South Rim Drives. Wildlife watching is a central reason to visit: Lamar Valley in the northeast is consistently the park's best area for spotting wolves and bison herds, particularly at dawn and dusk. Hayden Valley between Fishing Bridge and Canyon harbors large bison herds, bears, and river otters. Mammoth Hot Springs in the north features white and cream travertine terraces deposited by carbonate-rich geothermal water. The Grand Loop Road links all major thermal areas and covers roughly 140 miles. Allow at least three to four days to visit the main areas; a full week suits those combining major sights with backcountry hiking.