Ascendancy of the Mule

Mules gradually displaced oxen and horses as the work-engines of small, southern farms as the 19th century progressed:

"By the twentieth century, mules were a standard fixture on southern cotton farms and plantations of all sizes. The number of mules in the region increased until 1925, when nearly four-fifths of the mules in the United States were in the South ... the mule remained a constant, as well as a central, aspect of southern agricultural identity. This is evidenced by the fact that farm size in the South was often based on the measure of a one-mule farm or a two-mule farm." -- George B. Ellenberg, Mule South to Tractor South: Mules, Machines, and the Transformation of the Cotton South