CarbineCaleb, the pic you posted was of a mountain goat,
Oreamnos americanus. These are considered as natural and indigenous. Mountain goats are in the same family as domesticated (now feral) goats as are sheep, cattle, bison, etc. Feral most often refers to those animals that have become domesticated and that have then returned to the wild in some manner, often in places where they are not indigenous. For example, the domesticated pig common to farms here in the US are the species
Sus scrofa. They are said to be feral when they have gotten loose and then returned to their pre-domestication behaviors in the wild. There are many examples such as feral dogs and cats, for example.
In relation to BuzzKill's query and mention of feral goats in Ireland, those goats were domesticated, taken to Ireland, and are now considered feral because of their return to the wild.
Lewis & Clark ran across these a little over 2 centuries ago, and Meriweather Lewis, a naturalist trained by Thomas Jefferson, immediately correctly classified them as goats. For some odd reason, we've always incorrectly called 'em "antelope" -- Pronghorn Antelope, to be [im]precise. They range from west Texas to Nevada to Montana, and are not just feral-- they're wild.
Long Path, pronghorn antelope most definitely not goats. Lewis' identification was in error. You are correct in that they are not true antelope. Then again, pandas are not bears either. The name assigned to antelope pertains to resembling antelope, not being antelope, as with the pandas. Pandas are in the raccoon family (Procyonidae) and not the bear family (Ursidae). American Antelope are in the family Antelocapridae. True antelope are in the family Bovidae along with sheep, goats, cattle, bison, etc.
Pronghorn are unique and are the sole surviving member of an ancient family dating
back 20 million years. They are set apart from goats and other bovids quite readily as the Pronghorn is the only animal in the world with branched horns (not antlers)
and the only animal in the world to shed its horns, as if they were antlers.
Ord classified and scientifically described pronghorn in 1815.
Lewis may have been trained by Jefferson, but neither had the fossil record information to trace the evolutionary ancestry of the pronghorn and bovids to know if they belonged together or not.