The buffalo remaining in the neighborhood during the winter were mostly old bulls, too lean to eat; and as the snows came on most of the antelope left for the rugged country farther west, swimming the Missouri in great bands.

Before the bitter weather began the explorers were much interested by the methods of the Indians in hunting, especially when they surrounded and slaughtered bands of buffalo on horseback; and by the curious pens, with huge V-shaped wings, into which they drove antelope.
They Start Westward in the Spring.
In the spring of 1805, Lewis and Clark again started westward, first sending down-stream ten of their companions, to carry home the notes of their trip so far, and a few valuable specimens.

The party that started westward numbered thirty-two adults, all told; for one sergeant had died, and two or three persons had volunteered at the Mandan villages, including a rather worthless French "squaw-man," with an intelligent Indian wife, whose baby was but a few weeks old.
From this point onwards, when they began to travel west instead of north, the explorers were in a country where no white man had ever trod.
It was not the first time the continent had been crossed.

The Spaniards had crossed and recrossed it, for two centuries, farther south.

In British America Mackenzie had already penetrated to the Pacific, while Hearne had made a far more noteworthy and difficult trip than Mackenzie, when he wandered over the terrible desolation of the Barren Grounds, which lie under the Arctic circle.