Pronghorns are members of the order Artiodactyla- even-toed ungulates. From there, they also belong to the Infraorder Pecora, which they share with antelope, cattle, goats, giraffes, etc. But that's were any taxonomic similarities to other living species ends. Pronghorns are the only extant species in the family Antilocapridae. There are nearly two dozen completely extinct genera in the family, and only Antilocapra remains.
Antilocapra americana has a number of different subspecies, all of which live in the Western United States and Canada. They stand about three feet at the shoulder, and both males and females have those characteristic backwards facing horns. Pronghorns are the fastest land animals in North America, and can sprint at speed of nearly 60mph. Even more awesome is the fact that they are also build for long distance running, though the speed are not nearly as high. Pronghorns communicate by sight. They have excellent vision, and when danger is spotted, they signal by raising white hairs on their rump.
Pronghorns also hold the second place title for longest migration of any North American land animal. Some herds (not all, some have enough food to stay in place year round) move 300 miles round trip between Wyoming's Green River Basin and Grand Teton National Park. This move now places the Pronghorn under multiple man-made threats, including cars and fences. The National Wildlife Federation is working to create Corridors to help these migrations.