Slideshow: American bison thunder back from brink of extinction

Centuries ago, as many as 60 million bison roamed North America.

But greed and government policy almost wiped out these magnificent creatures in the 19th century. To businessmen and the U.S. government, the beasts got in the way of westward expansion and served as a valuable source of food and clothing for Native Americans, who were then considered to be enemies. The Army encouraged hunters' efforts to kill millions of them.

This evening on America Tonight, correspondent Chris Bury reports on the tortured past of the American bison, its salvation from extinction and how part of the Old West lives on in the annual bison roundup at Custer State Park in South Dakota.

Get a sneak peek of some striking images from his report and learn more about the history of bison in the slideshow above.