Two oxen pull a wagon on the Oregon Trail.
An ox, also known as a bullock, is an animal that is often used for pulling or carrying heavy items.
On March 3, 1850, Marty McFly, Jules Brown, and Verne Brown disguised the DeLorean time machine as a covered wagon.
When Daniel Clayton and Martha O'Brien's wagon train arrived, with various animals carrying the wagons, including horses, mules, and oxen. They let them join the wagon train, and lent them two mules.