Bighorn sheep (Ovis canadensis) is a species of sheep in North America named for its large horns. These horns can weigh up to 30 pounds (14 kg), while the sheep themselves weigh up to 300 pounds (140 kg).
From Illustrated Childrens Map of Animals of the World:
Sheep originally crossed to North America over the Bering land bridge from Siberia: the population in North America peaked in the millions, and the bighorn sheep entered into the mythology of Native Americans.
Big Ram Rumble (NatGeo video):