We saw pronghorns in both Yellowstone & Grand Teton national parks (I took this photo in Yellowstone). Contrary to what you may think from their appearance, they are not antelopes, but are part of the superfamily Giraffoidea, which includes only three living species - the other two being giraffes & okapis. From Wikipedia: "The pronghorn is the fastest land mammal in the Western Hemisphere, being built for maximum predator evasion through running. The top speed is very hard to measure accurately and varies between individuals; it can run 35 mph for 4 mi (56 km/h for 6 km), 42 mph for 1 mi (67 km/h for 1.6 km); and 55 mph for 0.5 mi (88.5 km/h for .8 km). It is often cited as the second-fastest land animal, second only to the cheetah. It can, however, sustain high speeds longer than cheetahs." Please zoom.