Oxen were simply bulls of various breeds, such as Hereford, Longhorn, line-back, or shorthorn crossbreeds developed for muscle and strength. They could have been reddish or brown or spttted. They were castrated young to make them more manageable and were at their best between 5 and 8 years of age, but could be useful for twice that long. Young and/or untrained oxen presented plenty of problems to the teamsters. They grew to about 2,000 pounds. [Beef cattle are slaughtered at about half that weight.] Oxen were yoked in pairs, with two to four pair per wagon. The teamster would walk on the left and often carried a shoulder-length staff called a "Moses Stick" by which he or she could use to help guide, encourage, or punish an ox. The commands were "gee" (head or turn right), "haw" (head or turn left), and "whoa" (stand still or stop). European emigrants, with their accents and lack of experience, had a hard time controlling oxen, especially at first.
Oxen were slower than mules or horses but were cheaper, survived on prairie grass better, and had better stamina. Their normal speed of two mile per hour was a comfortable speed for the thousands who walked along with the wagons. They suffered exhaustion, starvation, thirst, poisonous water, and sore feet. Many died in the yoke. Others during the night. Sometimes booties were made to wrap an ox's sore feet. Campsites were chosen with the animals in mind.
Horses and mules were better at plowing. Except for a hobby or for living history sites, there is no market for oxen, as the pioneers knew them, to be bred. This means that seeing one is a relatively rare experience.
The U.S. 1850 Census reported 1.17 million oxen in the nation. That number dropped more than a half million to 1.17 million by 1890 (with 720,767 in the West).