After the American Revolution ended, when Charls III, King of Spain, wanted to make friends with George Washington, he knew he had to send him som thing good in the mail. Som thing fancy. Som thing valuable. Som thing that no one else in the world had.
Did Charls send gold? No. Did he send jewelrys? No. What about a fancy sword with Washington's name wrote on the handle? NO.
Charls sent George Washington a mammoth Spanish jack donkey, so that he could start making draft mules like yours truly. And in conclusion, that is why we have the Fourth of July, to celebrate mules in America. It's a fact, you can look it up on the internets.