Stock cars, or “cattle cars” were used to transport livestock, like cows, sheep, and pigs, from remote farms and ranch lands to centralized stockyards and processing facilities.  Cowboys on horseback would round-up a herd of cattle and ‘drive’ them to a railroad siding where the animals would be loaded into the train cars for the trip to market.  While ‘stock cars’ could be used to transport a variety of animals, some railroads also had specialized cars, designed for carrying pigs, circus animals or race horses.