Oxen as Spare Tires

“A yoke of oxen is two animals leashed together by a yoke: a crossbar of carved wood fastened to their necks with oxbows. Two or three yoke (four to six animals) pulled a typical emigrant wagon. Most emigrants brought along several additional animals—the nineteenth-century equivalent of spare tires. Of oxen, mules, and horses (the three animal engines of the westward migration) oxen were by far the most common. Although slow, oxen were relatively inexpensive, immensely strong, less likely than horses or mules to be stolen by Indians, and could subsist reasonably well on available grass.”