Early on in their travels with the Corps of Discovery, as they headed to the Platte River, passing big bluestem meadows and cottonwoods along the riverbanks, brothers Rueben and Joseph Field captured a wolf cub. They tied it up, planning to make it a pet. It turned out to be easier to catch a wolf than to keep one. It quickly gnawed its way free and scampered back into the wild. Lewis and Clark called the gray wolf the "large wolf" to distinguish it from the smaller coyotes, which they dubbed the "prairie wolf."

Wolves were familiar from the East, but Lewis and Clark discovered a subspecies, the plains gray wolf, or Canis lupus nubilus. As usual, Lewis offered detailed observations, noting how a pack would isolate an antelope from the herd so they could chase it down. Clark wrote, "The large Wolves are very numerous," and they saw them throughout the western part of their trip, feeding on bison and stalking wild turkeys. They heard them howling through the night.