Back in the early days of our country, most folks were, to some degree, engaged in farming. The Founding Fathers and our early Presidents were no exception; most of them owned farms or plantations from which they earned the bulk of their incomes, as public service paid very little in those days and there were no pensions.
One of these worthies, James Madison, was the principal author of the Constitution, served in Congress and as Secretary of State under President Thomas Jefferson, and then was elected the fourth President of the United States, leading the nation during the War of 1812. Madison had inherited his father's estate, a 2750-acre tobacco plantation near Orange, Virginia, that was (and still is) called Montpelier.
After the end of his Presidency in 1817, Madison retired to Montpelier and took a keen interest in his crops and livestock as he tried to restore the long-neglected plantation to a profitable operation.
In 1818, Madison addressed the Albemarle Agricultural Society, of which he was then the president, on the subject of "Why Farmers Should Use Oxen Rather than Horses." He started out by saying, "I cannot but consider it as an error in our husbandry, that oxen are too little used in place of horses."
A span of Milking Shorthorn oxen named Herschel and Walker and owned by Tillers International of Scotts, Michigan, pull a plow at the 2013 Horse Progress Days in Clare, Michigan. (Photo by Sam Moore)
The complete address is too wordy to quote in full, besides being written in the flowery, over-blown (at least to modern ears) style of the early 19th century, so I'll paraphrase the main points as follows:
After making his case for oxen over horses, Madison closed his address with the following: "The mule seems to be, in point of economy between the ox and the horse; preferable to the latter, inferior to the former; but so well adapted to particular services, that he may find a proper place on many farms. He is liable to the objection which weighs most against the ox. He is less fitted than the horse for road service."
I can't imagine why Madison felt the mule wasn't suited for "road service," but that's what he said.