Idaho Falls, ID
On the Snake River Plain at 4,744ft MSL. Class D, single 9,002ft runway 3/21. The closest commercial airport to Idaho National Laboratory (originally the National Reactor Testing Station, established 1949), 50 miles west, where the world's first electricity from nuclear power was generated by Experimental Breeder Reactor I in December 1951. The INL site is 890 square miles of high desert — the largest contained federal research facility in the US — and operated 52 different experimental reactors between 1949 and 1975. Idaho Falls itself grew from a Mormon-pioneer river crossing into a city of 65,000, largely on INL employment. Yellowstone's west entrance is 100 miles north.
The Teton Range rises 7,000 feet directly out of Jackson Hole valley with no foothills — one of the steepest mountain fronts in North America. Grand Teton, the highest peak at 13,775 feet, was first summited in 1898; the range was named by French-Canadian trappers who called the three central peaks "les trois tétons" ("the three breasts"), a name that has not aged well but stuck. The Snake River runs along the eastern base of the range; from Jackson Hole Airport (KJAC, the only commercial airport inside a US national park) the entire range fills the western horizon. Glaciers — Teton, Schoolroom, Middle Teton, Falling Ice — still cling to the upper cirques despite a century of retreat.
A vast ocean of black lava on the Snake River Plain, so strange that NASA sent Apollo astronauts here in 1969 to learn the basics of volcanic geology before walking on the actual Moon. The lava isn't from a single volcano but from the Great Rift, a deep crack in the Earth that has erupted repeatedly over the last 15,000 years (most recently about 2,000 years ago, and geologists expect it will again). The result is 600 square miles of cinder cones, spatter cones, lava tubes, and frozen black flows dotted with islands of sagebrush — an otherworldly moonscape in the middle of Idaho. You can hike Inferno Cone for a 360° view over the flows, or descend into lava-tube caves where ice survives the summer.
The first national park in the world (1872), 3,468 square miles straddling the Wyoming-Montana-Idaho border. Yellowstone sits over the Yellowstone hotspot — a magma plume that has produced three caldera-forming "supervolcano" eruptions in the last 2.1 million years, the most recent 640,000 years ago. The current caldera is 30 by 45 miles. Geothermal features result: 10,000+ hot springs, 500+ geysers (more than the rest of the world combined), Old Faithful erupting on a 90-minute cycle, the bright bacterial mats around Grand Prismatic Spring. The Yellowstone River carved the Grand Canyon of the Yellowstone with its 308-foot Lower Falls. Bison herd is the largest in the country (~5,000), grizzlies have returned to ~1,000, the wolves reintroduced in 1995 are at ~100. Most-visited national park in the US most years. From the air, the Upper Geyser Basin reads as a white mineral-stained clearing in the forest, with steam plumes visible 50-plus miles out on cool mornings; Grand Prismatic Spring shows its rainbow banding best from directly overhead.
The Yellowstone caldera is one of the largest active volcanic systems on Earth. The Upper Geyser Basin, containing Old Faithful and 150+ other geysers, appears from altitude as a white mineral-stained clearing in the forest with steam plumes visible from 50+ miles on cool mornings. The Grand Prismatic Spring (the largest hot spring in the US) shows its rainbow colors best from directly above. Yellowstone National Park has standard NPS overflight advisories.