Postcard with a Farmer Guiding Oxen, circa 1910

Oxen were the main source of power on many farms before the development of portable steam and internal combustion engines. Under yoke, as shown here, they could haul a wide range of heavy objects: logs and boulders; vehicles, like wagons; or agricultural equipment, like plows. Using specially designed treadmills, oxen could also power stationary machinery in barns or farmyards.