In this episode, we visit one of the most iconic national parks in the United States: Yellowstone. Megan Kate Nelson talks to us about how Yellowstone came to be a park, as well as how all the amazing geothermal features and animals came to be in the area.

Guest bio: Megan Kate Nelson

Megan Kate Nelson was born and raised in Colorado; she is now a writer and historian living in  Massachusetts. She earned her BA from Harvard University in History and Literature and her PhD from Iowa in American Studies. She taught at Texas Tech, Cal State Fullerton, Harvard, MIT, and Brown before leaving academia to become a full-time writer in 2014. 

Her most recent book, The Three-Cornered War: The Union, the Confederacy, and Native Peoples in the Fight for the West, was published by Scribner in February 2020. This project was the recipient of a 2017 NEH Public Scholar Award and a Filson Historical Society Fellowship, and was chosen as a Top Ten History Book of 2020 by Smithsonian Magazine, and a 2020 Best Book in Civil War History by Civil War Monitor. In March 2022, Scribner will publish her next book, This Strange Country, which tells the story of the creation of Yellowstone National Park in the context of Reconstruction.

Dr. Nelson is the author of two previous books: Ruin Nation: Destruction and the American Civil War (Georgia, 2012) and Trembling Earth: A Cultural History of the Okefenokee Swamp (Georgia, 2005). She writes about the Civil War, the U.S. West, and American culture for The New York TimesWashington PostThe AtlanticSmithsonian MagazinePreservation Magazine, and Civil War Times. Her column on Civil War popular culture, “Stereoscope,” appears regularly in the Civil War Monitor


Maggie: Hey, have you ever taken a big road trip?

Abby: Yeah, I have. When I was a very little kid—I think I was two—my family drove all the way to Montana from South Carolina. We stopped in St. Louis, but our real destination was Yellowstone National Park. And then when I graduated from college, we basically did that whole road trip again.

Maggie: Wow, that sounds super fun. Can we do that?

Abby: Maybe someday soon!

Maggie: Why did your family want to go to Yellowstone?

Abby: I think we wanted to go because it’s such an amazing place with tons of cool animals, and also incredibly beautiful and pretty bizarre landscapes. And I have to say it definitely did not disappoint.

Maggie: Yellowstone is what we’re talking about today on

Maggie and Abby: Big If True,

Maggie: where I, Maggie,

Abby: and I, Abby,

Maggie: explore the truth about big things. Yellowstone has a lot of things called geothermal features. “Geo” means “earth” or “ground,” and “therm” means “heat.” Geothermal features are things that get their heat from inside the earth. So here’s our quiz question for today.

Vocabulary Term: geothermal

of, relating to, or utilizing the heat of the earth’s interior

Merriam-Webster Dictionary

Abby: How many of the Earth’s geothermal features are in Yellowstone?

A: 5%, B: 8%, C: 27%, or D: 50%?

Abby: We’ll tell you the answer near the end of the show. Today, we’ve got a guest to tell us all about Yellowstone, both past and present. She’s a historian who wrote a book about the history of the park.

Megan Kate Nelson: I am Megan Kate Nelson. I am a historian and writer. And I live outside Boston on the traditional homelands of the Wampanoag people.

Maggie: What is Yellowstone?

Nelson: So Yellowstone is a national park. It is a huge area—when it was first created, no one could believe how big the park was—about almost 4000 square miles. And it sits kind of in the middle of an even bigger ecosystem that’s about 28,000 square miles. And it’s because the American government preserved Yellowstone back in 1872, that this enormous ecosystem exists in Wyoming and Idaho and Montana. And what that means is it’s a very stable ecosystem. And that means that because humans have not been allowed to really build over it or develop it in any way, really, except for tourism, nature has been allowed to develop all of its biodiversity without interference. But it is, it is so unusual and unique because it is a volcanic area. So Yellowstone basin, which we think of when we think about Yellowstone, which has all the geysers and the mud pots, in addition to mountains, beautiful mountains and waterfalls, and rivers and lakes, it is known as a caldera, which is really just basically a big crater of a volcano that is still active underground.

Vocabulary word: caldera

a volcanic crater that has a diameter many times that of the vent and is formed by collapse of the central part of a volcano or by explosions of extraordinary violence

Merriam-Webster Dictionary

Nelson: So there is a huge pool, we don’t know how big it is actually, of molten lava that is bubbling and heating up the earth under Yellowstone, and it is heating up water and pushing it to the surface, which is why we’re getting all of these cool things.

Maggie: Why is it called Yellowstone?

Nelson: It is called Yellowstone, actually, after the river, one of several major rivers that have their headwaters in that basin. Back in the early 18th century, French traders who were going up and down the Missouri River trading with native peoples came upon the confluence of the Yellowstone River and the Missouri and, they saw there a bunch of yellow rocks which had been stained that color from the sulfur from the basin and basically called it in French, Yellowstone. And then that’s the term that made it into the books. That’s not what the Lakota peoples of that region call it. They call it the Elk River for the animals that proliferate along that valley. But the Yellowstone is what stuck in the French and then also the Anglo American mind.

Maggie: What made all the sulfur pools and the geysers and all the stuff that makes Yellowstone so interesting?

Nelson: In order to get a geothermal region like Yellowstone, you need to have three components. You need to have that volcanic magma pool that I was talking about, that’s kind of boiling and bubbling away that’s fairly close to the surface, or at least closer than maybe we would like it to be. And then ample rain and snowfall, and the Yellowstone region has that because it’s so high up in elevation that the snowstorm start very early, and there’s lots of snowpack, and so you get a lot of water coming down into the rivers. There are lots of lakes and lots of groundwater in the region, and it gets pretty good rainfall also. And then when Yellowstone was first forming, which the whole area was formed 2 million years ago, but the caldera was formed in this giant volcanic eruption many 1000s of times the power of Mount St. Helens, that that created the caldera 640,000 years ago. And when that happened, and over the years where there’s been erosion and different other forms of geological change, it created all these cracks and fissures kind of from the magma pools up to the surface. And the scientists call this the the plumbing, which is a hilarious term but but it’s an accurate term, it helps you visualize it, right? Where the magma pool is, is kind of down underneath, and then the, the water is collecting above it, and the series of channels and cracks. And as it heats up, it turns into steam and gets pushed toward the surface. And so that expresses itself in a bunch of different kinds of ways and places that you would see in Yellowstone. If it’s just kind of gentle, steady pressure, then you’ll see a hot spring, if there’s just a very narrow fissure and not a lot of pressure, you might just see a steam vent or what they call a fumarole. But if it’s a greater pressure, if there’s a deeper system or more channels, and it’s kind of pushing through with a little more force, then that’s where you get a geyser. And depending on what kind of rock it’s moving through, it can look very different. So there are some pools that are very brightly colored, because they have lichen, or they have sulfur in the water in that part of the park.

Photo by Andrew Garland

Nelson: Or if it’s moving through clay instead of rock, that’s where you get the mud pots, which are the you know, bubbly. And it kind of bubbles up and, and when the scientists were exploring in 1871, they saw mud pots that would throw mud, like fairly long distances into the trees. So there were these trees that were just covered with dried mud like all around these areas, which they were really fascinated by. And of course, then they broke off limbs of them to take home with them as specimens and send them to the Smithsonian. When the surveyors were there in 1871, these guys were just going right up to the edge of all these features. And they said that when they lay down at night, they could hear the water bubbling under their head. They were collecting samples from the pools themselves, so they were crawling on their bellies up to the edge of all of these hot springs and mud pots and reaching out and dipping their vials. And there were a couple of times when a couple scientists including Ferdinand Hayden, who is the leader of the survey, they did break through the crust and fall in and Ferdinand Hayden fell in, up to kind of his knees, but he had leather boots on, and they protected his legs for a little bit for him to scramble out. So he wasn’t, he said that he was scalded but not, wasn’t horribly injured. But I was just surprised that more people didn’t follow through because they were taking great risks. They were taking it so always stay on the path. This is your public service announcement. Always stay on the marked pathways! Do not stray from them.

Maggie: What kinds of animals live in Yellowstone?

Nelson: Most famously, I think is the the bison herd.

Photo by Andrew Garland

Nelson: But then there are also large elk herds. There are grizzly bears and black bears.

Photo by Andrew Garland

Nelson: There are also wolves, which had been reintroduced into Yellowstone. They were eradicated in the 1920s because ranchers and farmers who lived on the edges of the park kind of hunted them down because they the wolves were killing their cattle. So in the 1920s, the wolf disappeared from Yellowstone, but the scientists reintroduced them in 1995. So now there are about 100 wolves. The animal, though, that the surveyors were most enchanted with, were the antelopes. They mostly live in the West and they live in in fairly large herds. And they’re kind of small, and they’re very fast. And so they appear they’re very curious and they like to see what you’re up to. So they come close. But if you try to approach them or you know, like a lot of these early explorers were trying to hunt them for food, they could rarely do it because the antelopes are really, really fast. So those are kind of the big groups, but there are also lynxes and coyotes and foxes and beavers and animals that you might be familiar with.

Maggie: When did Yellowstone become a national park?

Nelson: It became a national park on March 1 1872, signed into being by President Ulysses S. Grant.

Maggie: Why did Yellowstone become a national park?

Nelson: This is an excellent question. It became a national park for a couple of reasons. First of all, there was this scientific exploration in 1871. And it was led by this guy named Ferdinand Hayden, who was a geologist who had been making surveys for the federal government for a couple of years before that point.

Group of members of the Survey, made while in camp at Red Buttes. Natrona County, Wyoming. 1870. Photo from U.S. Geological Survey.

Nelson: And Yellowstone was the one of the last remaining unmapped places on mapped by Americans. And so he really wanted to see it; he got money from Congress to go and explore it. And once he saw it, and they had returned, you know, he really wanted to keep going back and keep using it as a scientific laboratory for understanding all kinds of interesting questions about geology, how old the earth was, how the earth evolved, why it looks the way it does. And so that was part of it, is that Hayden was very interested in this idea, saving it as a national park. Then there were the business interests. In both Montana, there were business boosters, and then in Philadelphia, there was a railroad man named Jay Cooke, who was building the Northern Pacific Railroad, to connect the Great Lakes to the Pacific coast. And he thought that his railroad might go within about 50 miles of Yellowstone. And so they worked together, all the scientists, the the Montana boosters, the business boosters, and Jay Cooke’s railroad people, to lobby members of Congress to pass this Act, which they did. And one other important element is that, you know, this was in the early 1870s. So it was in the wake of the American Civil War, and the country was still pretty unstable. So they were looking for something to unify Americans to have a space for all Americans to go. And as they put it, to recreate themselves, or we can see it as re-create themselves. It was something that was this collective endeavor, that was for the pursuit of knowledge and for understanding different elements of science. And people became really interested in captivated in it and followed it as, as something to kind of take their their mind away maybe to a different kind of place, which is I think, something we’re all looking forward to when the when the pandemic ends.

Maggie: Why is it good to preserve land like this? Or does it matter?

Nelson: I think it does matter. I think it’s really good to preserve a place like this, to help nature to help nature reestablish itself to have all that good biodiversity and to have kind of healthy environments. And I think it’s also a good thing for science that we can learn about all kinds of animal life. We can learn about waters and rivers and lakes and and what kind of creates them and what sustains them. And then also, Yellowstone is the largest geothermal field in the world. There are other places that have geyser systems and hot springs in South America, or Russia and New Zealand. But Yellowstone has 50% of the entire world’s features. So this is a really important place to learn about all of that volcanic action and its role in in shaping the world.

Maggie: Hey, there’s the answer to our quiz question: Yellowstone has an astonishing 50% of the world’s geothermal features! That’s a lot of heat coming up from the earth!

Abby: And it means that the diversity of the plants and animals in the area is pretty remarkable. So listeners, we want to know: have you been to Yellowstone? What was your favorite part? And if you haven’t been, do you want to go?

Maggie: You can tell us on social media. You can find us on Facebook or Instagram, or you can send us an email. All that info is on our website and that’s our show. Join us next time for another episode of Big If True.


Big If True is produced by me and Maggie. Special thanks to our guest this episode, Megan Kate Nelson. To learn more about her check out our show notes at Our music is by Andrew Cote, and a special shout-out to Yellowstone National Park for making public a huge library of sounds from the park that you heard in this episode. And shout out to you—thanks for listening!

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