The short answer
Yellowstone National Park covers about 3,472 square miles by the National Park Service’s figure, which it says has not been scientifically verified; 96 per cent is in the northwestern corner of Wyoming, with smaller parts in Montana and Idaho. President Ulysses S. Grant signed the act creating it on 1 March 1872, and the National Park Service describes it as the beginning of a worldwide national park movement. It sits on a volcanic plateau, and the U.S. Geological Survey counts more than 10,000 thermal features in it: hot springs, geysers, steam vents and mud pots. The Park Service puts the geysers at more than 500, which it says is more than half the world’s geysers. The Park Service lists 27 tribes with historic and modern connections to the land. Most roads are open to cars from late spring to early autumn; the road across the north of the park stays open all year.
From Tally’s diary
Steam coming out of the ground on a frosty morning, and a smell of boiled eggs. I walked the planks over pools of a blue I have no word for, with orange and green slime running out of them in bands, while a shaggy bison strolled through the steam. Something in the ground went off like a kettle and everyone cheered. I cheered too, then went back to the slime.
Why it's worth knowing
The colours around Yellowstone’s hot springs, the orange, yellow, brown and green that band outward from the blue centres, are not minerals. They are mats of microbes, each band a community suited to a different temperature as the water cools on its way out of the spring. The hottest centres are too hot for anything that photosynthesises. Before the 1960s, biologists did not expect much to live in water that hot at all.
November 2016Orange and yellow thermophile mats where hot spring water runs out across the ground.
Photograph: NPS / Neal Herbert, Public domain, cropped
Thomas Brock, a microbiologist at Indiana University, first noticed the life in the springs on a visit in 1964. In August 1966 he came back with colleagues and students, among them Hudson Freeze, then an undergraduate. The U.S. Geological Survey’s Yellowstone Volcano Observatory records that Freeze isolated a new bacterium from a sample taken at Mushroom Pool, a small hot spring in the Great Fountain Group of the Lower Geyser Basin. Brock and Freeze described it in the Journal of Bacteriology in 1969 as Thermus aquaticus, strain YT-1, and deposited it in the American Type Culture Collection.
Two decades later, the biochemist Kary Mullis needed an enzyme that could copy DNA at the high temperatures his new method used. The Park Service’s account is that Mullis found Brock’s Mushroom Pool culture in the American Type Culture Collection, a colleague bought some, and the heat-proof DNA polymerase grown from it, Taq, made the polymerase chain reaction fast and cheap. The DNA testing now used in medical diagnosis and criminal investigation runs, in large part, on an enzyme from a hot spring most Yellowstone visitors never see.
The park had no share in what followed. Hoffmann-La Roche bought the PCR and Taq patents from Cetus, Mullis’s employer, for $330 million, and the Park Service came to call the episode “the Great Taq Rip-off”. In the late 1990s Yellowstone signed a research agreement with a biotechnology company, Diversa, and after an environmental impact statement that Yellowstone led, the Park Service issued a Record of Decision in March 2010 to apply benefits-sharing across the national parks: research on a park’s organisms can now carry an agreement to send a share of later earnings back to the park.
The field notes
Mushroom Pool
Mushroom Pool is small and plain by Yellowstone’s standards. The Yellowstone Volcano Observatory notes that its name may date from the 1890s, given either for its shape or for the algae and bacteria in it, and that it was off the beaten path and not a visitor destination, though close enough to a road for researchers to reach. Sources name it both Mushroom Pool and Mushroom Spring; the Park Service and the Geological Survey use Mushroom Pool.
Thermal features in Yellowstone are protected, and visitors must keep to boardwalks and marked trails in thermal areas. The crust around a spring can be thin, and the water beneath it is near boiling. Mushroom Pool is not on a boardwalk; the mats that made it famous can be seen instead in the runoff channels of springs that are.
From a culture collection to a laboratory staple
The polymerase chain reaction copies a chosen stretch of DNA over and over by heating and cooling a mixture, and each heating step destroyed the ordinary enzymes then available, which had to be added again. An enzyme from a bacterium that lives in near-boiling water survives the heating. Taq polymerase was first isolated in 1976, and Thermus aquaticus grows best at 70 °C.
Mullis shared the 1993 Nobel Prize in Chemistry for the invention of PCR. The University of Wisconsin–Madison, where Brock later worked, has held the discovery up as a paragon of basic science.
The rest of the hot ground
The Geological Survey counts more than 10,000 thermal features, and the Park Service more than 500 geysers among them. Mushroom Pool lies in the Lower Geyser Basin. Old Faithful is in the Upper Geyser Basin, and Grand Prismatic Spring, ringed with the same kinds of microbial mat, is in the Midway Geyser Basin between the two.
August 2013Old Faithful erupting above the Upper Geyser Basin, with the Old Faithful Inn beyond.
Photograph: NPS / Jim Peaco, Public domain, cropped
The heat comes from the volcanic system beneath the plateau. It is the reason the springs exist and the reason the park is watched continuously by the Yellowstone Volcano Observatory.
Whose park
The Park Service lists 27 tribes with historic and modern connections to the lands now inside Yellowstone. Its own history says that for tribes such as the Blackfeet, Crow, Kiowa, Nez Perce, Cheyenne and Shoshone-Bannock, the closing off of the park meant the loss of hunting grounds, living space and lands of great spiritual significance. In 1864 a group of Piegan Blackfeet guided a Jesuit, Xavier Kuppens, to the geysers they already knew.
June 2021Morning steam over the Lower Geyser Basin.
Photograph: NPS / Diane Renkin, Public domain, cropped
September 2014A double rainbow in the mist at the Lower Falls of the Yellowstone River, seen from Uncle Tom's Trail.
Photograph: NPS / Neal Herbert, Public domain, cropped
June 2018Bison grazing in the Lamar Valley at sunrise.
Photograph: NPS / Jacob W. Frank, Public domain
- Stay on the boardwalk, every step. The crust is thin and the water would cook you.
- Look at the edges of the pools, not only the middles, where the colours run out in bands. Then find out what they are.
- Give the bison the whole road. They will take it anyway.
- Walk it as a guest. This ground was somebody's long before it was a park, and it still means a great deal to them.
- Wait for the famous spout. (Waited. Added several other spouts while waiting. The list is now mostly spouts.)
A relic from Yellowstone
Relic, entry 92Sample taken: August 1966Strain: Thermus aquaticus YT-1
Mushroom Pool. A small hot spring in the Great Fountain Group of the Lower Geyser Basin, named, perhaps in the 1890s, for its shape or for what grew in it. It has no boardwalk and no crowd, and the rules that protect Yellowstone’s thermal ground keep visitors away from it. In 1966 a sample from it yielded Thermus aquaticus, strain YT-1, and from that strain came the enzyme behind the modern DNA test. Almost nobody who visits Yellowstone sees it, and almost everybody who has had a PCR test owes it something.
Tally, in the marginA plain little pool off the path that nobody photographs, and it turned out to be the important one. I had been on the side of the quiet pools all day, and I am now insufferable about it.
Getting there
- 1
Five ways in
Yellowstone has five entrances.
- 2
Airports and gateway towns
Airports serving the park include Bozeman in Montana and Cody and Jackson in Wyoming, and gateway towns such as Gardiner, West Yellowstone and Cody sit at the entrances.
- 3
Slow driving inside the park
Distances inside the park are long and speed limits are low, so allow more time than the map suggests.
- 4
The year-round northern road
The road from the North Entrance through Mammoth Hot Springs to the Northeast Entrance is open all year.
- ✓
| J | F | M | A | M | J | J | A | S | O | N | D |
|---|---|---|---|---|---|---|---|---|---|---|---|
| May: best time | June: best time | July: best time | August: best time | September: best time |
- Late spring to early autumn, when the park roads are open
When to go. Most park roads close to cars from early November, reopen in stages from mid-April and are fully open by late spring, weather permitting. The road from the North Entrance through Mammoth Hot Springs to the Northeast Entrance is open all year. In winter, from mid-December, the interior is reached by snowcoach and guided snowmobile only.
What it costs. The park charges an entrance fee. Rooms inside the park are few and go early; the gateway towns have more.
In the thermal areas. Boardwalks and marked trails cross the thermal ground, and the water is near boiling. The park posts the distances it requires from bison, elk and bears.
For wildlife watchers
- Who lives here
- Spring brings bison calving and wolf pups leaving their dens in the Lamar Valley; the bison rut runs through the Lamar and Hayden valleys in July and August, and the elk rut comes to Mammoth Hot Springs in September and October.Source: National Park Service (Yellowstone seasons) · read
- How many
- Yellowstone has 67 mammal species, among them seven native hoofed species and two bear species.Source: National Park Service (Yellowstone wildlife) · read
Wildlife calendar
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Bison calves born in the Lamar Valley: April to May.
Source: National Park Service (Yellowstone seasons) · read
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Bison rut in the Lamar and Hayden valleys: July to August.
Source: National Park Service (Yellowstone seasons) · read
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Elk rut at Mammoth Hot Springs: September to October.
Source: National Park Service (Yellowstone seasons) · read
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Wolf watching in the Lamar Valley: March and November to December.
Source: National Park Service (Yellowstone seasons) · read
- Visitor rule
- The Park Service says approaching on foot within 100 yards (91 m) of bears or wolves, or within 25 yards (23 m) of other wildlife, is prohibited.Source: National Park Service (Yellowstone wildlife) · read
Mark this place
The passport stamp for this place.
Common questions
What is Thermus aquaticus and where was it found in Yellowstone?
Thermus aquaticus is a bacterium that thrives in near-boiling water. Hudson Freeze, an undergraduate working with the microbiologist Thomas Brock of Indiana University, isolated it from a sample taken in August 1966 at Mushroom Pool, a small hot spring in the Great Fountain Group of Yellowstone’s Lower Geyser Basin. Brock and Freeze named it in the Journal of Bacteriology in 1969.
How did Yellowstone contribute to PCR?
The polymerase chain reaction needs an enzyme that survives repeated heating. Kary Mullis, according to the National Park Service, found Thomas Brock’s Yellowstone culture of Thermus aquaticus in the American Type Culture Collection; the heat-proof enzyme grown from it, Taq polymerase, made PCR fast and cheap. Mullis shared the 1993 Nobel Prize in Chemistry for the method.
Can you visit Mushroom Pool in Yellowstone?
Not up close. Mushroom Pool, where Thermus aquaticus was found in 1966, is a small hot spring in Yellowstone’s Lower Geyser Basin that the U.S. Geological Survey describes as off the beaten path and not a visitor destination. Yellowstone’s rules keep visitors on boardwalks and marked trails in thermal areas, and the same kinds of microbial mats can be seen from the boardwalks elsewhere.
Why are Yellowstone's hot springs so colourful?
The orange, yellow, brown and green bands around Yellowstone’s hot springs are mats of heat-loving microbes, according to the National Park Service and the U.S. Geological Survey. Each band holds a community suited to a particular temperature as the water cools away from the centre. The hottest centres are too hot for photosynthesising microbes, which is why they stay clear and blue.
Did Yellowstone earn money from Taq polymerase?
No. Hoffmann-La Roche bought the PCR and Taq patents from Cetus for $330 million, according to Wikipedia, and Yellowstone had no agreement entitling it to a share. The park later signed a research agreement with the biotechnology company Diversa, and in March 2010 the National Park Service issued a Record of Decision, prepared with Yellowstone in the lead, to apply benefits-sharing across the national parks for discoveries made through park research permits.
When did Yellowstone become a national park?
President Ulysses S. Grant signed the act establishing Yellowstone National Park on 1 March 1872. The National Park Service describes Yellowstone’s founding as the start of a worldwide national park movement. The park covers about 3,472 square miles by the Park Service’s figure, mostly in Wyoming, with parts in Montana and Idaho.
How many geysers and hot springs are in Yellowstone?
The U.S. Geological Survey counts more than 10,000 thermal features in Yellowstone National Park, including hot springs, geysers, steam vents and mud pots. The National Park Service puts Yellowstone’s geysers at more than 500, which it says is more than half the world’s geysers.
When are Yellowstone's roads open?
Most of Yellowstone’s roads close to cars in early November and reopen in stages from mid-April into late spring, weather permitting. The road between the North Entrance, Mammoth Hot Springs and the Northeast Entrance is open all year. From mid-December the interior is reached only by snowcoach or guided snowmobile, according to the National Park Service.
Photographs on this page
Tap a photograph to see it full size.
Photograph: NPS / Jacob W. Frank, Public domain
Photograph: NPS / Neal Herbert, Public domain, cropped
Photograph: NPS / Jim Peaco, Public domain, cropped
Photograph: NPS / Diane Renkin, Public domain, cropped
Photograph: NPS / Neal Herbert, Public domain, cropped
Photograph: NPS / Jacob W. Frank, Public domain
