At the time America was discovered by Europeans, it was estimated that 30 to 60 million bison ranged this area. In 1870 this number had been reduced to 5.5 million. In the days of pioneer travel great bison herds, wading streams, sometimes halted a boat in midstream or, moving over the prairies, blocked and occasionally even derailed a train.

The westward-moving pioneers and railroad workers wantonly killed the huge animals by the thousands for food. Only the choicest pieces of the slaughtered bison, the hump and tongues, were cut out of the carcasses. By the 1880s fewer than a thousand were left on the continent, two thirds of them in Canada. By the 1990s there were about 120,000 bison left, kept mostly on privately owned ranches and on government preserves.

For the Plains Indians the bison was the most important game animal. Its hide furnished material for tepees and robes; its meat was eaten fresh or preserved as pemmican by drying and pounding.

The forepart hair is permanent, but the hair on the hind portions is shed annually, beginning in March. By early summer these parts are quite bare and very sensitive. For protection against insect bites a bison wallows in muddy sloughs or shallow ponds. The wallowing covers its body with mud or clay. When this dries in the sun it forms a protecting cover.

The new hair is well grown by October, and it is at its best in November and December. The hide then is valuable as fur. Before the bison became nearly extinct, overcoats made of the fur of young bison were in common use and were inexpensive.

The bison's horns are short and black. In the male they are thick at the base and taper abruptly to sharp points as they curve outward and upward; the female's horns are more slender. The hoofs are black.

Routes were the same year after year. The southward movement was made usually in single file. Bison trails in some places were worn as much as 3 feet (1 meter) deep. The northward movement began in the spring, after the calves were strong enough for travel. In this movement the herds were smaller. The bulls ranged in an outer circle around the cows and calves. When threatened, the herd bunched, and the bulls faced outward toward the danger. Ice weakened by the spring sun would sometimes break under the weight of a migrating herd and drown the animals.

The European bison (Bos taurus), the wisent, is also sometimes called aurochs. They flourished in Europe centuries ago. Until World War I, 1,500 head were kept in preserves in the Caucasus and in Lithuania by the Russian czar. They are now almost extinct. A few remain in the wilds of Poland and the Caucasus and in European zoos. They should not be confused with the extinct giant ox (Bos primigenius), or urus, of Europe, which were also known as aurochs. The European bison are a little larger than the American bison. They once ranged in small herds.