Well, this is a broad question, so I'm not quite sure what answer you're looking for, but the simplest answer, which used to get me confused, is: the monomer is a repeat unit of the polymer. Let's start by analyzing the words monomer and polymer. Mono = one, and poly = many. Now, lets go back to the science.
History of the United States with 150+ answers. According to one source: Twelve American presidents owned slaves, eight while serving in office, and at least 25 presidents count slave owners among their ancestors.. http://www.slate.com/articles/li... However, to put this into perspective this would be 37 that were either slave owners themselves or descended from slave owner ancestors - or 84%.
At the time of his death in 1799, George Washington owned some 300 slaves. However, before his passing, he had become opposed to slavery, and in his will he ordered that his slaves to be freed after his wife's death.