Reptile
Prairie Rattlesnake
Crotalus viridis
Photo: Unknown, CC BY-SA 2.5
Common Names
Rattlesnake / Prairie Rattlesnake
Habitat
Great Falls
Conservation
Apparently secure
First Observed
1805-04-26
Observed At
Mouth of the Yellowstone River, near present-day Fort Buford, North Dakota
Lewis awoke from a nap under a tree to find a prairie rattlesnake coiled a few feet away on the tree’s leaning trunk.
In the NPS atlas of species the expedition described
Prairie rattlesnake
Lewis awoke from a nap under a tree near Great Falls to find a prairie rattlesnake coiled a few feet away on the tree’s leaning trunk.
Partially sourced from the National Park Service, Lewis and Clark National Historic Trail Park Atlas.
Recent sightings
Where it’s being seen today
5 research-grade iNaturalist observations between 2021–2025. Most recent: 2025-09-06. Sourced from Terrain360 trail captures, cached locally.
Journal References
11 journal entries mention Prairie Rattlesnake
May
16
1805
Clark: May 16, 1805
...y recently. Capt. Clark narrowly escaped being bitten by
a rattlesnake in the course of his walk, the party killed one this evening
at our encampment, which he informed ...
Jun
15
1805
Lewis: June 15, 1805
...n colour. when I awoke from my sleep
today I found a large rattlesnake coiled on the leaning trunk of a tree
under the shade of which I had been lying at the distance of...
Aug
14
1805
Lewis: August 14, 1805
... labour. they encamped this evening on Lard. side near
the rattlesnake clift
Aug
15
1805
Lewis: August 15, 1805
...Lard. Capt Clark was very near being bitten twice
today by rattlesnakes, the Indian woman also narrowly escaped. they caught
a number of fine trout. Capt. Clark killed a...
Aug
15
1805
Camp Fortunate / Shoshone contact — John Ordway: August 15, 1805
...by land, above the mouth of Black
Tail Deer Creek.
2 Modern Rattlesnake Creek. Coues.
3 Fourteen miles by water, 65 miles by land. Lewis places the camp four
land miles be...
Aug
16
1805
Lewis: August 16, 1805
... found the river so
difficult that he had halted below the Rattlesnake bluffs. I knew that if
these people left me that they would immediately disperse and secrete
them...
Mar
11
1806
Lewis: March 11, 1806
...and brought with him. The reptiles of this country are the
rattlesnake garter snake and the common brown Lizzard. The season was so
far advanced when we arrived on this ...
Apr
25
1806
Lewis: April 25, 1806
...e of the duckandmallard. saw many common lizzards,
several rattlesnakes killed by the party, they are the same as those
common to the U States. the horned Lizzard is als...
May
16
1806
Lewis: May 16, 1806
...t is 3 feet 11 Inches in length, is much
the colour of the rattlesnake common to the middle atlantic states, it has
no poisonous teeth. it has 218 scutae on the abdomen ...
May
30
1806
Lewis: May 30, 1806
...The reptiles which I have observed
in this quarter are the Rattlesnake of the speceis discribed on the
Missouri, they are abundant in every part of the country and are t...
Aug
4
1806
Lewis: August 4, 1806
...ble distance North. during our halt we killed a very large
rattlesnake of the speceis common to our country. it had 176 scuta on the
abdomen and 25 on the tail, it's len...
