September 14, 1804, near mouth of Ball Creek, Lyman County, South Dakota.
A medium-size, deerlike mammal. Upper body pale tan or reddish tan; chest, belly, inner legs, cheeks and lower jaw, sides, and rump patch are white. Height: 35–41 in (88–103 cm); length: 4.1–4.8 ft (1.3–1.5 m); tail: 2.4–6.8 in (6–17 cm). Weight: male 90–140 lb (41–64 kg), female 75–105 lb (34–48 kg).
Grasslands, grassy brushlands, and particularly bunchgrass-sagegrass areas.
Southeastern Oregon, southern Idaho, southern Alberta, southern Saskatchewan, Montana, and western North Dakota south to Arizona and western Texas.
The fastest animal in the Western Hemisphere and among the fastest in the world, it has been clocked at 70 mph (110 km/h) for three to four minutes at a time.
"In my walk I Killed a Buck Goat [antelope] of this Countrey, about the hight of the Grown Deer, its body Shorter... the Colour is a light gray with black behind its ears down its neck... Verry actively made, has only a pair of hoofs to each foot, his brains on the back of his head, his Norstrals large, his eyes like a Sheep he is more like the Antilope or Gazella of Africa than any other Species of Goat."
Lewis—Monday, September 17, 1804
"We found the Antelope extreemly shye and watchfull insomuch that we had been unable to get a shot at them; when at rest they generally seelect the most elivated point in the neighbourhood, and as they are watchfull and extreemely quick of sight and their sense of smelling very accute it is almost impossible to approach them within gunshot... they will frequently discover and flee from you at the distance of three miles [4.8 kilometers]. I had this day an opportunity of witnessing the agility and the superior fleetness of this anamal which was to me really astonishing... I beheld the rapidity of their flight along the ridge before me it appeared reather the rappid flight of birds than the motion of quadrupeds."