WASHINGTON — President Obama signed a law on Monday making the bison — tens of millions of which once roamed North America — the country’s first national mammal.

The designation does nothing to threaten the bald eagle’s position as the national animal. But the eagle is not a mammal. So, at long last, the nation now has an official one.

The bison’s territory once stretched from the forests of Alaska to the grasslands of Mexico. The animal remains the largest mammal in North America, with mature bulls weighing up to a ton. Despite their size, the animals are surprisingly quick, reaching speeds of up to 35 miles per hour.

They were not fast enough, however, to outrun bullets, and their extraordinary size and tendency to travel in herds made them easy targets for hunters during the 19th century. Native American tribes survived on bison by following herds, and massacres of the animals helped push Indian cultures into collapse.