Cimarron by Edna Ferber

By noon next day they were wondering how they had got on at all without him. He gathered wood. He started fires. He tended Cim like a nurse, played with him, sang to him, helped put him to bed, slept anywhere, like a little dog. He even helped Sabra to drive her team, change and change about, for after all there was little to it but the holding of the reins slackly in one's fingers while the horses plodded across the prairie, mile on mile, mile on mile.

Yancey pointed out the definiteness with which the land changed when they left Kansas and came into the Oklahoma country. "Oklahoma," he explained to Cim. "That's Choctaw. Okla -- people. Humma -- red. Red People. That's what they called it when the Indians came here to live."