In centuries long past, a vast swath of grassland swept down the center of North America, from Canada's Prairie Provinces to central Texas. This once-plentiful prairie has now all but disappeared. Humans have grazed, mowed, and plowed the plains, dammed the rivers, and imposed their will on the land and its creatures. Fortunately, some remnants have survived, including the Joseph H. Williams Tallgrass Prairie Preserve in northeastern Oklahoma...