The pronghorn (Antilocapra americana) is often mistakenly called an antelope. Though it looks a bit like the African antelope in appearance, it is actually an ancient native North American species. Its closest living relative, oddly enough, is the giraffe.
The fastest land mammal in North America, pronghorn can reach speeds of nearly 60 miles per hour. The males grow horns with two or so prongs, hence their name.
Find these speedsters in the northern reaches of Yellowstone. Look in sagebrush meadows near the North Entrance in the Gardiner area and in Lamar Valley. Look for their bright coats of white and rusty tan.
Thanks to Mike McCoy for helping out here.