This 21-cent definitive stamp features a powerful and dignified portrait of an American Bison. The bison, often called a buffalo, is a story of national tragedy and triumph. Numbering in the tens of millions, they were the keystone species of the Great Plains, central to the lives of many Native American tribes. In the 19th century, they were slaughtered by the millions, and by the 1880s, fewer than 1,000 remained. The first day of issue at Yellowstone National Park holds deep significance. The small, isolated herd that found refuge in the park's remote Pelican Valley was instrumental in saving the species from complete annihilation. Today, Yellowstone is home to the nation's largest free-roaming bison population. This stamp is more than just a depiction of an animal; it is a recognition of a profound conservation success story and a tribute to the enduring spirit of the American West.