The Yellowstone National Park Stamp

Where Yellowstone is

Yellowstone, for people who count parks

Signed March 1, 1872, by Ulysses S. Grant. It is almost always called the first national park in the world, and that is defensible with one qualifier: older protected areas exist, including a forest reserve in Tobago from 1776, but Yellowstone was the first area created as a national park by a national government and kept under federal control. Every park that came after followed this template. Wyoming did not become a state until 1890.

Nobody funded it, so it nearly got stripped. Civilian superintendents from 1872 to 1886 had no money, no staff and no enforcement power. Poachers shot the wildlife. Souvenir hunters broke pieces off the geyser cones. When Congress refused to appropriate operating funds in 1886, the Interior Secretary called in the Army. The cavalry arrived that August and stayed until 1918. Their headquarters at Mammoth Hot Springs is the park headquarters today.

About the volcano. The caldera runs roughly 45 by 28 miles. There have been three caldera-forming eruptions, the most recent about 631,000 years ago. USGS puts the annual odds of another at about one in 730,000, comparable to a large asteroid strike, and states plainly that Yellowstone is not overdue, because volcanoes do not run on schedules. The magma chamber is only 5 to 15% molten, which is too little for a supereruption. The current alert level is normal. The real hazards are smaller and more frequent: one to three thousand earthquakes a year, almost all imperceptible, and occasional hydrothermal explosions like the one at Biscuit Basin in July 2024.

More than 10,000 hydrothermal features and over 500 geysers, which is the largest concentration on Earth. You will often see "more than half the world's geysers," but neither NPS nor USGS makes that claim in their own words, so treat it as an estimate rather than a fact.

The most dangerous thing here is the water. Since 1872 the hot springs have killed 22 people. Bears have killed 8 and bison 2. It is not close.

Official Yellowstone park site (nps.gov)

What lives in Yellowstone

Wolves, and the argument about what they did. Fourteen wolves from Alberta were released in 1995 and seventeen more in 1996. There are now at least 108 in ten packs inside the park. The famous version of what followed says wolves frightened elk out of the riverbanks, willows and aspen recovered, beavers came back, and the rivers changed course. That story is genuinely disputed in the scientific literature and has been for fifteen years. A 2010 study in Ecology found aspen were not recovering even with a large wolf population present. Other researchers found water table depth mattered more than wolves, and that elk in high-predation areas were not frightened enough to stop browsing. What everyone agrees on: elk numbers on the northern range fell sharply after 1995, and nobody has isolated how much of that was wolves versus drought, hunting outside the park, grizzlies, cougars and hard winters. It is a better story for being unresolved.

Bison, the only continuously wild herd in the lower 48. Down to roughly two dozen animals in 1902, now near 5,300. The Park Service is careful with the wording: this is the only place in the lower 48 states with a free-ranging bison population that has persisted since prehistoric times.

And bison are what actually hurt people. The Park Service states it flatly: bison have injured more people in Yellowstone than any other animal. A peer-reviewed study counted 25 bison injuries between 2000 and 2015. Bear injuries, by contrast, are down to about one every five years since 1980, from roughly 45 a year in the mid-century. A bison runs about three times faster than you do. Stay 25 yards from bison and elk, 100 from bears and wolves.

Grizzlies, back from 136. That was the count in 1975 when they were listed as threatened. There are now around 1,030 in the Greater Yellowstone Ecosystem and 150 to 200 inside the park. The collapse in bear attacks traces to one decision: closing the garbage dumps in 1970 and securing human food.

The Yellowstone designs

Old Faithful and the Inn

The geyser is faithful, not punctual. The median interval is about 102 minutes but the real range runs from 54 to 118, and rangers predict it by timing how long the previous eruption lasted. It has been getting slower: earthquakes in 1959, 1983 and 1998 each stretched the average. The Inn behind it went up in a single winter in 1903, six stories of lodgepole pine with deliberately gnarled limbs used as railings, and it more or less invented the rustic style that shaped park lodges everywhere after.

Grand Prismatic Spring

The largest hot spring in Yellowstone, roughly 300 feet across and over 120 feet deep. The rings are living things. The center is too hot for almost anything, so it shows the deep blue of very pure, very deep water. Moving outward as it cools, mats of heat-loving microbes take over in bands, yellow then orange then rust. In summer they make more orange pigment as sun protection, so the colors are strongest in the season everyone visits.

Grand Canyon of the Yellowstone and Lower Falls

The falls drop 308 feet, nearly twice the height of Niagara's Horseshoe Falls, into a canyon that is only ten to fourteen thousand years old. The yellow walls are not sulfur, which is the common guess. They are rhyolite that an ancient hot-spring system chemically altered, leaving iron behind. In the Park Service's own phrase, the canyon is rusting.

How to record your Yellowstone visit

Yellowstone, asked and answered