Bison are the largest land mammals in North America, often weighing over 1 ton. Readers discover this and other amazing facts about bison as they also see full-color photographs of these massive mammals. Science concepts, such as life cycles and natural habitats, are presented in an engaging way, through accessible text, graphic organizers, and fun fact boxes. Bison once roamed the Great Plains by the millions, but now there are only a small number of them left in North America. Why did their population decrease so dramatically? The answer is waiting for readers to uncover.