Pompeys Pillar National Monument

In honor of the 50th anniversary of the National Trails System four special dogs, the Lewis and Clark Pups, will travel in the paws of their ancestor Seaman, dog of Meriwether Lewis. The pups will travel more than 3,700 miles to complete their mission to commemorate and protect the Lewis and Clark National Historic Trail. As they make their stops they will be reporting back in on their adventures. Follow Rocky, Harper, Dakota, and Keelie on their adventures on the Newfie News Blog.

Pompeys Pillar is a High Potential Historic Site on the Lewis and Clark National Historic Trail.
stuffed pup at Pompeys Pillar
Pompeys WHAT? Where’s the Pillar?

“At 4 P.M., I arrived at a remarkable rock...This rock which I shall call Pompy’s Tower is 200 feet high, and 400 paces in circumference.” -William Clark, July 25 1806.

Hello world! Keelie Pup checking in at Pompeys Pillar National Monument. Wow! That IS a remarkable rock, but where is the Pillar? Oh, that big rock is Pompeys Pillar? That is funny. I thought Clark named it Pompy’s Tower. Hmmm… I’d better do a little digging. Well, it turns out, Captain Clark did call it Pompy’s Tower when he wrote about it in his journal, but when his journal was published in 1814, the name was changed to Pompeys Pillar. The park ranger told me that historians believe that the Pillar was named after Sacagawea’s young son, and that Clark referred to him as “his little dancing boy, Pomp.”

sutffed dog by river
Today, I learned that the Lewis and Clark Expedition separated into two groups for a while when they were on their way home. So Meriwether Lewis (and my illustrious foredog, Seaman) took folks to explore the Marias River farther north. William Clark went southeast to explore the Yellowstone River (my personal favorite). He had all sorts of misadventures on his way. He didn’t get to meet any Native Americans on the Yellowstone, but they sure knew he was there. Somehow, all of Clark’s 49 horses disappeared, and found new homes. I don’t think that would have happened if my great-great-great-great-grandpa had been there...
Stuffed dog in canoe
Anyway, I learned that Clark made two canoes out of cottonwood trees and that is how he got to Pompeys Pillar!

Stuffed pup near rock carving
I got to go up the Pillar on a boardwalk to see where Captain Clark etched his name. I was amazed to see it was still so visible.
William clark signature carved
I read in his journal that he left his name, the day of the month, and the year.
interpretive sign
I also learned that he was not the first person to leave his mark on the Pillar. He saw the figures of people and animals painted on the rock (pictographs)! The rock art is older, so it has weathered a lot. But ask a ranger or a Friend of Pompeys Pillar to show you some of the pictographs and petroglyphs.
close up of rock tower
When I was at Pompeys Pillar National Monument, I learned that the natural history is an integral part of the Pillar’s significance. You see, Pompeys Pillar stands out. It is all by itself on the south side of the Yellowstone River. Even pups like me are fascinated, but I am a rockhound…
Can you see the different layers of the Pillar? These are made up of different kinds of sediments: sand and silt. What’s the difference? Well, the size of the sediment is the difference. Sand is larger, so when scientists see sandstone at Pompeys Pillar, they see the remnants of an ancient river whose current was very fast and carried away finer silt and mud, leaving only sand. The thickest layers of Pompeys Pillar are sandstone. Sometimes, that current slowed WAY down, and dropped those fine sediments that eventually formed a rock called shale. Shale layers on the Pillar look a lot like dirt clods. I talked to a paleontologist while at Pompeys Pillar, and he told me that when you look at the Pillar, every time the rock changes, it indicates something happened at that time that changed the ancient environment in some way.
After the sediment was laid down by the old river, time and pressure eventually created the rock layers you see today. Then the river moved back and forth across the valley, and washed away the rock connecting the Pillar to the rest of the cliffs. I did not know that water was so powerful, but it is! It created Pompeys Pillar, but it will someday turn the Pillar back into a beach…

interpretive sign
Sometimes, plants and animals would get trapped in the ancient river, and become fossils. In the interpretive center at Pompeys Pillar, I discovered that Captain Clark found a fossil just down the river from Pompeys Pillar. I did a little “digging” in the journal of William Clark and found this:
“…I employed myself in getting pieces of the rib of a fish which was cemented within the face of the rock. This rib is about 3 inches in circumference about the middle. It is 3 feet in length though part of the end appears to have been broken off. I have several pieces of this rib. The bone is neither decayed nor petrified but very rotten.” –July 25, 1806

view of rock pillar with goose
Pompeys Pillar is also a good place to see all sorts of living critters. It may not look like the houses that you and I know, but the Pillar is home to many different birds and mammals. Right away, I saw a goose and a yellow-bellied marmot. There are so many animals here because Pompeys Pillar sits smack dab between two different environments: the river and the plains. Where these two ecosystems come together, you find an incredible diversity of plants and animals.
stuffed pup near Pompeys Pillar National Monument sign
Here I am at the Pompeys Pillar National Monument Interpretive Center. It is quiet now, but soon it humming with activity. I discovered so many things in the visitor center. I learned about Clark’s “rib of a fish” here, and about the importance of the site to Native American tribes of the Northern Plains. Did you know that people of the Crow tribe call Pompeys Pillar “The Place Where the Mountain Lion Lies”? I also learned about bullboats, “made in the Mandan style” by Sergeant Pryor when he was at Pompeys Pillar.
stuffed pup near river
Today, you can get to Pompeys Pillar National Monument a lot easier than Captain Clark did. In fact, you can follow in the footsteps of the Corps of Discovery all the way from Three Forks, Montana to Pompeys Pillar National Monument, and east almost to North Dakota without even leaving Interstate 94. But what fun is that? I like to get out and explore, and you can too. If you really want to relive the experience, paddle your own canoe or kayak to Pompeys Pillar National Monument, like William Clark did. But don’t take a bullboat. It is hair-raising! I yelped all the way down the river…
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Last updated: May 18, 2018